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Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 4865 |
1 files changed, 4865 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c new file mode 100644 index 000000000..327844fed --- /dev/null +++ b/fs/namei.c @@ -0,0 +1,4865 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/namei.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + */ + +/* + * Some corrections by tytso. + */ + +/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname + * lookup logic. + */ +/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. + */ + +#include <linux/init.h> +#include <linux/export.h> +#include <linux/kernel.h> +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/pagemap.h> +#include <linux/fsnotify.h> +#include <linux/personality.h> +#include <linux/security.h> +#include <linux/ima.h> +#include <linux/syscalls.h> +#include <linux/mount.h> +#include <linux/audit.h> +#include <linux/capability.h> +#include <linux/file.h> +#include <linux/fcntl.h> +#include <linux/device_cgroup.h> +#include <linux/fs_struct.h> +#include <linux/posix_acl.h> +#include <linux/hash.h> +#include <linux/bitops.h> +#include <linux/init_task.h> +#include <linux/uaccess.h> +#include <linux/build_bug.h> + +#include "internal.h" +#include "mount.h" + +/* [Feb-1997 T. Schoebel-Theuer] + * Fundamental changes in the pathname lookup mechanisms (namei) + * were necessary because of omirr. The reason is that omirr needs + * to know the _real_ pathname, not the user-supplied one, in case + * of symlinks (and also when transname replacements occur). + * + * The new code replaces the old recursive symlink resolution with + * an iterative one (in case of non-nested symlink chains). It does + * this with calls to <fs>_follow_link(). + * As a side effect, dir_namei(), _namei() and follow_link() are now + * replaced with a single function lookup_dentry() that can handle all + * the special cases of the former code. + * + * With the new dcache, the pathname is stored at each inode, at least as + * long as the refcount of the inode is positive. As a side effect, the + * size of the dcache depends on the inode cache and thus is dynamic. + * + * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink + * resolution to correspond with current state of the code. + * + * Note that the symlink resolution is not *completely* iterative. + * There is still a significant amount of tail- and mid- recursion in + * the algorithm. Also, note that <fs>_readlink() is not used in + * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() + * may return different results than <fs>_follow_link(). Many virtual + * filesystems (including /proc) exhibit this behavior. + */ + +/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: + * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL + * and the name already exists in form of a symlink, try to create the new + * name indicated by the symlink. The old code always complained that the + * name already exists, due to not following the symlink even if its target + * is nonexistent. The new semantics affects also mknod() and link() when + * the name is a symlink pointing to a non-existent name. + * + * I don't know which semantics is the right one, since I have no access + * to standards. But I found by trial that HP-UX 9.0 has the full "new" + * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the + * "old" one. Personally, I think the new semantics is much more logical. + * Note that "ln old new" where "new" is a symlink pointing to a non-existing + * file does succeed in both HP-UX and SunOs, but not in Solaris + * and in the old Linux semantics. + */ + +/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink + * semantics. See the comments in "open_namei" and "do_link" below. + * + * [10-Sep-98 Alan Modra] Another symlink change. + */ + +/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: + * inside the path - always follow. + * in the last component in creation/removal/renaming - never follow. + * if LOOKUP_FOLLOW passed - follow. + * if the pathname has trailing slashes - follow. + * otherwise - don't follow. + * (applied in that order). + * + * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT + * restored for 2.4. This is the last surviving part of old 4.2BSD bug. + * During the 2.4 we need to fix the userland stuff depending on it - + * hopefully we will be able to get rid of that wart in 2.5. So far only + * XEmacs seems to be relying on it... + */ +/* + * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) + * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives + * any extra contention... + */ + +/* In order to reduce some races, while at the same time doing additional + * checking and hopefully speeding things up, we copy filenames to the + * kernel data space before using them.. + * + * POSIX.1 2.4: an empty pathname is invalid (ENOENT). + * PATH_MAX includes the nul terminator --RR. + */ + +#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname)) + +struct filename * +getname_flags(const char __user *filename, int flags, int *empty) +{ + struct filename *result; + char *kname; + int len; + BUILD_BUG_ON(offsetof(struct filename, iname) % sizeof(long) != 0); + + result = audit_reusename(filename); + if (result) + return result; + + result = __getname(); + if (unlikely(!result)) + return ERR_PTR(-ENOMEM); + + /* + * First, try to embed the struct filename inside the names_cache + * allocation + */ + kname = (char *)result->iname; + result->name = kname; + + len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX); + if (unlikely(len < 0)) { + __putname(result); + return ERR_PTR(len); + } + + /* + * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a + * separate struct filename so we can dedicate the entire + * names_cache allocation for the pathname, and re-do the copy from + * userland. + */ + if (unlikely(len == EMBEDDED_NAME_MAX)) { + const size_t size = offsetof(struct filename, iname[1]); + kname = (char *)result; + + /* + * size is chosen that way we to guarantee that + * result->iname[0] is within the same object and that + * kname can't be equal to result->iname, no matter what. + */ + result = kzalloc(size, GFP_KERNEL); + if (unlikely(!result)) { + __putname(kname); + return ERR_PTR(-ENOMEM); + } + result->name = kname; + len = strncpy_from_user(kname, filename, PATH_MAX); + if (unlikely(len < 0)) { + __putname(kname); + kfree(result); + return ERR_PTR(len); + } + if (unlikely(len == PATH_MAX)) { + __putname(kname); + kfree(result); + return ERR_PTR(-ENAMETOOLONG); + } + } + + result->refcnt = 1; + /* The empty path is special. */ + if (unlikely(!len)) { + if (empty) + *empty = 1; + if (!(flags & LOOKUP_EMPTY)) { + putname(result); + return ERR_PTR(-ENOENT); + } + } + + result->uptr = filename; + result->aname = NULL; + audit_getname(result); + return result; +} + +struct filename * +getname(const char __user * filename) +{ + return getname_flags(filename, 0, NULL); +} + +struct filename * +getname_kernel(const char * filename) +{ + struct filename *result; + int len = strlen(filename) + 1; + + result = __getname(); + if (unlikely(!result)) + return ERR_PTR(-ENOMEM); + + if (len <= EMBEDDED_NAME_MAX) { + result->name = (char *)result->iname; + } else if (len <= PATH_MAX) { + const size_t size = offsetof(struct filename, iname[1]); + struct filename *tmp; + + tmp = kmalloc(size, GFP_KERNEL); + if (unlikely(!tmp)) { + __putname(result); + return ERR_PTR(-ENOMEM); + } + tmp->name = (char *)result; + result = tmp; + } else { + __putname(result); + return ERR_PTR(-ENAMETOOLONG); + } + memcpy((char *)result->name, filename, len); + result->uptr = NULL; + result->aname = NULL; + result->refcnt = 1; + audit_getname(result); + + return result; +} + +void putname(struct filename *name) +{ + BUG_ON(name->refcnt <= 0); + + if (--name->refcnt > 0) + return; + + if (name->name != name->iname) { + __putname(name->name); + kfree(name); + } else + __putname(name); +} + +static int check_acl(struct inode *inode, int mask) +{ +#ifdef CONFIG_FS_POSIX_ACL + struct posix_acl *acl; + + if (mask & MAY_NOT_BLOCK) { + acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); + if (!acl) + return -EAGAIN; + /* no ->get_acl() calls in RCU mode... */ + if (is_uncached_acl(acl)) + return -ECHILD; + return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); + } + + acl = get_acl(inode, ACL_TYPE_ACCESS); + if (IS_ERR(acl)) + return PTR_ERR(acl); + if (acl) { + int error = posix_acl_permission(inode, acl, mask); + posix_acl_release(acl); + return error; + } +#endif + + return -EAGAIN; +} + +/* + * This does the basic permission checking + */ +static int acl_permission_check(struct inode *inode, int mask) +{ + unsigned int mode = inode->i_mode; + + if (likely(uid_eq(current_fsuid(), inode->i_uid))) + mode >>= 6; + else { + if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { + int error = check_acl(inode, mask); + if (error != -EAGAIN) + return error; + } + + if (in_group_p(inode->i_gid)) + mode >>= 3; + } + + /* + * If the DACs are ok we don't need any capability check. + */ + if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) + return 0; + return -EACCES; +} + +/** + * generic_permission - check for access rights on a Posix-like filesystem + * @inode: inode to check access rights for + * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) + * + * Used to check for read/write/execute permissions on a file. + * We use "fsuid" for this, letting us set arbitrary permissions + * for filesystem access without changing the "normal" uids which + * are used for other things. + * + * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk + * request cannot be satisfied (eg. requires blocking or too much complexity). + * It would then be called again in ref-walk mode. + */ +int generic_permission(struct inode *inode, int mask) +{ + int ret; + + /* + * Do the basic permission checks. + */ + ret = acl_permission_check(inode, mask); + if (ret != -EACCES) + return ret; + + if (S_ISDIR(inode->i_mode)) { + /* DACs are overridable for directories */ + if (!(mask & MAY_WRITE)) + if (capable_wrt_inode_uidgid(inode, + CAP_DAC_READ_SEARCH)) + return 0; + if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) + return 0; + return -EACCES; + } + + /* + * Searching includes executable on directories, else just read. + */ + mask &= MAY_READ | MAY_WRITE | MAY_EXEC; + if (mask == MAY_READ) + if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) + return 0; + /* + * Read/write DACs are always overridable. + * Executable DACs are overridable when there is + * at least one exec bit set. + */ + if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) + if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) + return 0; + + return -EACCES; +} +EXPORT_SYMBOL(generic_permission); + +/* + * We _really_ want to just do "generic_permission()" without + * even looking at the inode->i_op values. So we keep a cache + * flag in inode->i_opflags, that says "this has not special + * permission function, use the fast case". + */ +static inline int do_inode_permission(struct inode *inode, int mask) +{ + if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { + if (likely(inode->i_op->permission)) + return inode->i_op->permission(inode, mask); + + /* This gets set once for the inode lifetime */ + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_FASTPERM; + spin_unlock(&inode->i_lock); + } + return generic_permission(inode, mask); +} + +/** + * sb_permission - Check superblock-level permissions + * @sb: Superblock of inode to check permission on + * @inode: Inode to check permission on + * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) + * + * Separate out file-system wide checks from inode-specific permission checks. + */ +static int sb_permission(struct super_block *sb, struct inode *inode, int mask) +{ + if (unlikely(mask & MAY_WRITE)) { + umode_t mode = inode->i_mode; + + /* Nobody gets write access to a read-only fs. */ + if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) + return -EROFS; + } + return 0; +} + +/** + * inode_permission - Check for access rights to a given inode + * @inode: Inode to check permission on + * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) + * + * Check for read/write/execute permissions on an inode. We use fs[ug]id for + * this, letting us set arbitrary permissions for filesystem access without + * changing the "normal" UIDs which are used for other things. + * + * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. + */ +int inode_permission(struct inode *inode, int mask) +{ + int retval; + + retval = sb_permission(inode->i_sb, inode, mask); + if (retval) + return retval; + + if (unlikely(mask & MAY_WRITE)) { + /* + * Nobody gets write access to an immutable file. + */ + if (IS_IMMUTABLE(inode)) + return -EPERM; + + /* + * Updating mtime will likely cause i_uid and i_gid to be + * written back improperly if their true value is unknown + * to the vfs. + */ + if (HAS_UNMAPPED_ID(inode)) + return -EACCES; + } + + retval = do_inode_permission(inode, mask); + if (retval) + return retval; + + retval = devcgroup_inode_permission(inode, mask); + if (retval) + return retval; + + return security_inode_permission(inode, mask); +} +EXPORT_SYMBOL(inode_permission); + +/** + * path_get - get a reference to a path + * @path: path to get the reference to + * + * Given a path increment the reference count to the dentry and the vfsmount. + */ +void path_get(const struct path *path) +{ + mntget(path->mnt); + dget(path->dentry); +} +EXPORT_SYMBOL(path_get); + +/** + * path_put - put a reference to a path + * @path: path to put the reference to + * + * Given a path decrement the reference count to the dentry and the vfsmount. + */ +void path_put(const struct path *path) +{ + dput(path->dentry); + mntput(path->mnt); +} +EXPORT_SYMBOL(path_put); + +#define EMBEDDED_LEVELS 2 +struct nameidata { + struct path path; + struct qstr last; + struct path root; + struct inode *inode; /* path.dentry.d_inode */ + unsigned int flags; + unsigned seq, m_seq; + int last_type; + unsigned depth; + int total_link_count; + struct saved { + struct path link; + struct delayed_call done; + const char *name; + unsigned seq; + } *stack, internal[EMBEDDED_LEVELS]; + struct filename *name; + struct nameidata *saved; + struct inode *link_inode; + unsigned root_seq; + int dfd; +} __randomize_layout; + +static void set_nameidata(struct nameidata *p, int dfd, struct filename *name) +{ + struct nameidata *old = current->nameidata; + p->stack = p->internal; + p->dfd = dfd; + p->name = name; + p->total_link_count = old ? old->total_link_count : 0; + p->saved = old; + current->nameidata = p; +} + +static void restore_nameidata(void) +{ + struct nameidata *now = current->nameidata, *old = now->saved; + + current->nameidata = old; + if (old) + old->total_link_count = now->total_link_count; + if (now->stack != now->internal) + kfree(now->stack); +} + +static int __nd_alloc_stack(struct nameidata *nd) +{ + struct saved *p; + + if (nd->flags & LOOKUP_RCU) { + p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved), + GFP_ATOMIC); + if (unlikely(!p)) + return -ECHILD; + } else { + p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved), + GFP_KERNEL); + if (unlikely(!p)) + return -ENOMEM; + } + memcpy(p, nd->internal, sizeof(nd->internal)); + nd->stack = p; + return 0; +} + +/** + * path_connected - Verify that a path->dentry is below path->mnt.mnt_root + * @path: nameidate to verify + * + * Rename can sometimes move a file or directory outside of a bind + * mount, path_connected allows those cases to be detected. + */ +static bool path_connected(const struct path *path) +{ + struct vfsmount *mnt = path->mnt; + struct super_block *sb = mnt->mnt_sb; + + /* Bind mounts and multi-root filesystems can have disconnected paths */ + if (!(sb->s_iflags & SB_I_MULTIROOT) && (mnt->mnt_root == sb->s_root)) + return true; + + return is_subdir(path->dentry, mnt->mnt_root); +} + +static inline int nd_alloc_stack(struct nameidata *nd) +{ + if (likely(nd->depth != EMBEDDED_LEVELS)) + return 0; + if (likely(nd->stack != nd->internal)) + return 0; + return __nd_alloc_stack(nd); +} + +static void drop_links(struct nameidata *nd) +{ + int i = nd->depth; + while (i--) { + struct saved *last = nd->stack + i; + do_delayed_call(&last->done); + clear_delayed_call(&last->done); + } +} + +static void terminate_walk(struct nameidata *nd) +{ + drop_links(nd); + if (!(nd->flags & LOOKUP_RCU)) { + int i; + path_put(&nd->path); + for (i = 0; i < nd->depth; i++) + path_put(&nd->stack[i].link); + if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { + path_put(&nd->root); + nd->root.mnt = NULL; + } + } else { + nd->flags &= ~LOOKUP_RCU; + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; + rcu_read_unlock(); + } + nd->depth = 0; +} + +/* path_put is needed afterwards regardless of success or failure */ +static bool legitimize_path(struct nameidata *nd, + struct path *path, unsigned seq) +{ + int res = __legitimize_mnt(path->mnt, nd->m_seq); + if (unlikely(res)) { + if (res > 0) + path->mnt = NULL; + path->dentry = NULL; + return false; + } + if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) { + path->dentry = NULL; + return false; + } + return !read_seqcount_retry(&path->dentry->d_seq, seq); +} + +static bool legitimize_links(struct nameidata *nd) +{ + int i; + for (i = 0; i < nd->depth; i++) { + struct saved *last = nd->stack + i; + if (unlikely(!legitimize_path(nd, &last->link, last->seq))) { + drop_links(nd); + nd->depth = i + 1; + return false; + } + } + return true; +} + +/* + * Path walking has 2 modes, rcu-walk and ref-walk (see + * Documentation/filesystems/path-lookup.txt). In situations when we can't + * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab + * normal reference counts on dentries and vfsmounts to transition to ref-walk + * mode. Refcounts are grabbed at the last known good point before rcu-walk + * got stuck, so ref-walk may continue from there. If this is not successful + * (eg. a seqcount has changed), then failure is returned and it's up to caller + * to restart the path walk from the beginning in ref-walk mode. + */ + +/** + * unlazy_walk - try to switch to ref-walk mode. + * @nd: nameidata pathwalk data + * Returns: 0 on success, -ECHILD on failure + * + * unlazy_walk attempts to legitimize the current nd->path and nd->root + * for ref-walk mode. + * Must be called from rcu-walk context. + * Nothing should touch nameidata between unlazy_walk() failure and + * terminate_walk(). + */ +static int unlazy_walk(struct nameidata *nd) +{ + struct dentry *parent = nd->path.dentry; + + BUG_ON(!(nd->flags & LOOKUP_RCU)); + + nd->flags &= ~LOOKUP_RCU; + if (unlikely(!legitimize_links(nd))) + goto out2; + if (unlikely(!legitimize_path(nd, &nd->path, nd->seq))) + goto out1; + if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { + if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) + goto out; + } + rcu_read_unlock(); + BUG_ON(nd->inode != parent->d_inode); + return 0; + +out2: + nd->path.mnt = NULL; + nd->path.dentry = NULL; +out1: + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; +out: + rcu_read_unlock(); + return -ECHILD; +} + +/** + * unlazy_child - try to switch to ref-walk mode. + * @nd: nameidata pathwalk data + * @dentry: child of nd->path.dentry + * @seq: seq number to check dentry against + * Returns: 0 on success, -ECHILD on failure + * + * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry + * for ref-walk mode. @dentry must be a path found by a do_lookup call on + * @nd. Must be called from rcu-walk context. + * Nothing should touch nameidata between unlazy_child() failure and + * terminate_walk(). + */ +static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned seq) +{ + BUG_ON(!(nd->flags & LOOKUP_RCU)); + + nd->flags &= ~LOOKUP_RCU; + if (unlikely(!legitimize_links(nd))) + goto out2; + if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq))) + goto out2; + if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref))) + goto out1; + + /* + * We need to move both the parent and the dentry from the RCU domain + * to be properly refcounted. And the sequence number in the dentry + * validates *both* dentry counters, since we checked the sequence + * number of the parent after we got the child sequence number. So we + * know the parent must still be valid if the child sequence number is + */ + if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) + goto out; + if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) { + rcu_read_unlock(); + dput(dentry); + goto drop_root_mnt; + } + /* + * Sequence counts matched. Now make sure that the root is + * still valid and get it if required. + */ + if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { + if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) { + rcu_read_unlock(); + dput(dentry); + return -ECHILD; + } + } + + rcu_read_unlock(); + return 0; + +out2: + nd->path.mnt = NULL; +out1: + nd->path.dentry = NULL; +out: + rcu_read_unlock(); +drop_root_mnt: + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; + return -ECHILD; +} + +static inline int d_revalidate(struct dentry *dentry, unsigned int flags) +{ + if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) + return dentry->d_op->d_revalidate(dentry, flags); + else + return 1; +} + +/** + * complete_walk - successful completion of path walk + * @nd: pointer nameidata + * + * If we had been in RCU mode, drop out of it and legitimize nd->path. + * Revalidate the final result, unless we'd already done that during + * the path walk or the filesystem doesn't ask for it. Return 0 on + * success, -error on failure. In case of failure caller does not + * need to drop nd->path. + */ +static int complete_walk(struct nameidata *nd) +{ + struct dentry *dentry = nd->path.dentry; + int status; + + if (nd->flags & LOOKUP_RCU) { + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; + if (unlikely(unlazy_walk(nd))) + return -ECHILD; + } + + if (likely(!(nd->flags & LOOKUP_JUMPED))) + return 0; + + if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) + return 0; + + status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); + if (status > 0) + return 0; + + if (!status) + status = -ESTALE; + + return status; +} + +static void set_root(struct nameidata *nd) +{ + struct fs_struct *fs = current->fs; + + if (nd->flags & LOOKUP_RCU) { + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + nd->root = fs->root; + nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq); + } while (read_seqcount_retry(&fs->seq, seq)); + } else { + get_fs_root(fs, &nd->root); + } +} + +static void path_put_conditional(struct path *path, struct nameidata *nd) +{ + dput(path->dentry); + if (path->mnt != nd->path.mnt) + mntput(path->mnt); +} + +static inline void path_to_nameidata(const struct path *path, + struct nameidata *nd) +{ + if (!(nd->flags & LOOKUP_RCU)) { + dput(nd->path.dentry); + if (nd->path.mnt != path->mnt) + mntput(nd->path.mnt); + } + nd->path.mnt = path->mnt; + nd->path.dentry = path->dentry; +} + +static int nd_jump_root(struct nameidata *nd) +{ + if (nd->flags & LOOKUP_RCU) { + struct dentry *d; + nd->path = nd->root; + d = nd->path.dentry; + nd->inode = d->d_inode; + nd->seq = nd->root_seq; + if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq))) + return -ECHILD; + } else { + path_put(&nd->path); + nd->path = nd->root; + path_get(&nd->path); + nd->inode = nd->path.dentry->d_inode; + } + nd->flags |= LOOKUP_JUMPED; + return 0; +} + +/* + * Helper to directly jump to a known parsed path from ->get_link, + * caller must have taken a reference to path beforehand. + */ +void nd_jump_link(struct path *path) +{ + struct nameidata *nd = current->nameidata; + path_put(&nd->path); + + nd->path = *path; + nd->inode = nd->path.dentry->d_inode; + nd->flags |= LOOKUP_JUMPED; +} + +static inline void put_link(struct nameidata *nd) +{ + struct saved *last = nd->stack + --nd->depth; + do_delayed_call(&last->done); + if (!(nd->flags & LOOKUP_RCU)) + path_put(&last->link); +} + +int sysctl_protected_symlinks __read_mostly = 0; +int sysctl_protected_hardlinks __read_mostly = 0; +int sysctl_protected_fifos __read_mostly; +int sysctl_protected_regular __read_mostly; + +/** + * may_follow_link - Check symlink following for unsafe situations + * @nd: nameidata pathwalk data + * + * In the case of the sysctl_protected_symlinks sysctl being enabled, + * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is + * in a sticky world-writable directory. This is to protect privileged + * processes from failing races against path names that may change out + * from under them by way of other users creating malicious symlinks. + * It will permit symlinks to be followed only when outside a sticky + * world-writable directory, or when the uid of the symlink and follower + * match, or when the directory owner matches the symlink's owner. + * + * Returns 0 if following the symlink is allowed, -ve on error. + */ +static inline int may_follow_link(struct nameidata *nd) +{ + const struct inode *inode; + const struct inode *parent; + kuid_t puid; + + if (!sysctl_protected_symlinks) + return 0; + + /* Allowed if owner and follower match. */ + inode = nd->link_inode; + if (uid_eq(current_cred()->fsuid, inode->i_uid)) + return 0; + + /* Allowed if parent directory not sticky and world-writable. */ + parent = nd->inode; + if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) + return 0; + + /* Allowed if parent directory and link owner match. */ + puid = parent->i_uid; + if (uid_valid(puid) && uid_eq(puid, inode->i_uid)) + return 0; + + if (nd->flags & LOOKUP_RCU) + return -ECHILD; + + audit_inode(nd->name, nd->stack[0].link.dentry, 0); + audit_log_link_denied("follow_link"); + return -EACCES; +} + +/** + * safe_hardlink_source - Check for safe hardlink conditions + * @inode: the source inode to hardlink from + * + * Return false if at least one of the following conditions: + * - inode is not a regular file + * - inode is setuid + * - inode is setgid and group-exec + * - access failure for read and write + * + * Otherwise returns true. + */ +static bool safe_hardlink_source(struct inode *inode) +{ + umode_t mode = inode->i_mode; + + /* Special files should not get pinned to the filesystem. */ + if (!S_ISREG(mode)) + return false; + + /* Setuid files should not get pinned to the filesystem. */ + if (mode & S_ISUID) + return false; + + /* Executable setgid files should not get pinned to the filesystem. */ + if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) + return false; + + /* Hardlinking to unreadable or unwritable sources is dangerous. */ + if (inode_permission(inode, MAY_READ | MAY_WRITE)) + return false; + + return true; +} + +/** + * may_linkat - Check permissions for creating a hardlink + * @link: the source to hardlink from + * + * Block hardlink when all of: + * - sysctl_protected_hardlinks enabled + * - fsuid does not match inode + * - hardlink source is unsafe (see safe_hardlink_source() above) + * - not CAP_FOWNER in a namespace with the inode owner uid mapped + * + * Returns 0 if successful, -ve on error. + */ +static int may_linkat(struct path *link) +{ + struct inode *inode = link->dentry->d_inode; + + /* Inode writeback is not safe when the uid or gid are invalid. */ + if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) + return -EOVERFLOW; + + if (!sysctl_protected_hardlinks) + return 0; + + /* Source inode owner (or CAP_FOWNER) can hardlink all they like, + * otherwise, it must be a safe source. + */ + if (safe_hardlink_source(inode) || inode_owner_or_capable(inode)) + return 0; + + audit_log_link_denied("linkat"); + return -EPERM; +} + +/** + * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory + * should be allowed, or not, on files that already + * exist. + * @dir_mode: mode bits of directory + * @dir_uid: owner of directory + * @inode: the inode of the file to open + * + * Block an O_CREAT open of a FIFO (or a regular file) when: + * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled + * - the file already exists + * - we are in a sticky directory + * - we don't own the file + * - the owner of the directory doesn't own the file + * - the directory is world writable + * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2 + * the directory doesn't have to be world writable: being group writable will + * be enough. + * + * Returns 0 if the open is allowed, -ve on error. + */ +static int may_create_in_sticky(umode_t dir_mode, kuid_t dir_uid, + struct inode * const inode) +{ + if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) || + (!sysctl_protected_regular && S_ISREG(inode->i_mode)) || + likely(!(dir_mode & S_ISVTX)) || + uid_eq(inode->i_uid, dir_uid) || + uid_eq(current_fsuid(), inode->i_uid)) + return 0; + + if (likely(dir_mode & 0002) || + (dir_mode & 0020 && + ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) || + (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) { + return -EACCES; + } + return 0; +} + +static __always_inline +const char *get_link(struct nameidata *nd) +{ + struct saved *last = nd->stack + nd->depth - 1; + struct dentry *dentry = last->link.dentry; + struct inode *inode = nd->link_inode; + int error; + const char *res; + + if (!(nd->flags & LOOKUP_RCU)) { + touch_atime(&last->link); + cond_resched(); + } else if (atime_needs_update(&last->link, inode)) { + if (unlikely(unlazy_walk(nd))) + return ERR_PTR(-ECHILD); + touch_atime(&last->link); + } + + error = security_inode_follow_link(dentry, inode, + nd->flags & LOOKUP_RCU); + if (unlikely(error)) + return ERR_PTR(error); + + nd->last_type = LAST_BIND; + res = inode->i_link; + if (!res) { + const char * (*get)(struct dentry *, struct inode *, + struct delayed_call *); + get = inode->i_op->get_link; + if (nd->flags & LOOKUP_RCU) { + res = get(NULL, inode, &last->done); + if (res == ERR_PTR(-ECHILD)) { + if (unlikely(unlazy_walk(nd))) + return ERR_PTR(-ECHILD); + res = get(dentry, inode, &last->done); + } + } else { + res = get(dentry, inode, &last->done); + } + if (IS_ERR_OR_NULL(res)) + return res; + } + if (*res == '/') { + if (!nd->root.mnt) + set_root(nd); + if (unlikely(nd_jump_root(nd))) + return ERR_PTR(-ECHILD); + while (unlikely(*++res == '/')) + ; + } + if (!*res) + res = NULL; + return res; +} + +/* + * follow_up - Find the mountpoint of path's vfsmount + * + * Given a path, find the mountpoint of its source file system. + * Replace @path with the path of the mountpoint in the parent mount. + * Up is towards /. + * + * Return 1 if we went up a level and 0 if we were already at the + * root. + */ +int follow_up(struct path *path) +{ + struct mount *mnt = real_mount(path->mnt); + struct mount *parent; + struct dentry *mountpoint; + + read_seqlock_excl(&mount_lock); + parent = mnt->mnt_parent; + if (parent == mnt) { + read_sequnlock_excl(&mount_lock); + return 0; + } + mntget(&parent->mnt); + mountpoint = dget(mnt->mnt_mountpoint); + read_sequnlock_excl(&mount_lock); + dput(path->dentry); + path->dentry = mountpoint; + mntput(path->mnt); + path->mnt = &parent->mnt; + return 1; +} +EXPORT_SYMBOL(follow_up); + +/* + * Perform an automount + * - return -EISDIR to tell follow_managed() to stop and return the path we + * were called with. + */ +static int follow_automount(struct path *path, struct nameidata *nd, + bool *need_mntput) +{ + struct vfsmount *mnt; + int err; + + if (!path->dentry->d_op || !path->dentry->d_op->d_automount) + return -EREMOTE; + + /* We don't want to mount if someone's just doing a stat - + * unless they're stat'ing a directory and appended a '/' to + * the name. + * + * We do, however, want to mount if someone wants to open or + * create a file of any type under the mountpoint, wants to + * traverse through the mountpoint or wants to open the + * mounted directory. Also, autofs may mark negative dentries + * as being automount points. These will need the attentions + * of the daemon to instantiate them before they can be used. + */ + if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | + LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && + path->dentry->d_inode) + return -EISDIR; + + nd->total_link_count++; + if (nd->total_link_count >= 40) + return -ELOOP; + + mnt = path->dentry->d_op->d_automount(path); + if (IS_ERR(mnt)) { + /* + * The filesystem is allowed to return -EISDIR here to indicate + * it doesn't want to automount. For instance, autofs would do + * this so that its userspace daemon can mount on this dentry. + * + * However, we can only permit this if it's a terminal point in + * the path being looked up; if it wasn't then the remainder of + * the path is inaccessible and we should say so. + */ + if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT)) + return -EREMOTE; + return PTR_ERR(mnt); + } + + if (!mnt) /* mount collision */ + return 0; + + if (!*need_mntput) { + /* lock_mount() may release path->mnt on error */ + mntget(path->mnt); + *need_mntput = true; + } + err = finish_automount(mnt, path); + + switch (err) { + case -EBUSY: + /* Someone else made a mount here whilst we were busy */ + return 0; + case 0: + path_put(path); + path->mnt = mnt; + path->dentry = dget(mnt->mnt_root); + return 0; + default: + return err; + } + +} + +/* + * Handle a dentry that is managed in some way. + * - Flagged for transit management (autofs) + * - Flagged as mountpoint + * - Flagged as automount point + * + * This may only be called in refwalk mode. + * + * Serialization is taken care of in namespace.c + */ +static int follow_managed(struct path *path, struct nameidata *nd) +{ + struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ + unsigned managed; + bool need_mntput = false; + int ret = 0; + + /* Given that we're not holding a lock here, we retain the value in a + * local variable for each dentry as we look at it so that we don't see + * the components of that value change under us */ + while (managed = READ_ONCE(path->dentry->d_flags), + managed &= DCACHE_MANAGED_DENTRY, + unlikely(managed != 0)) { + /* Allow the filesystem to manage the transit without i_mutex + * being held. */ + if (managed & DCACHE_MANAGE_TRANSIT) { + BUG_ON(!path->dentry->d_op); + BUG_ON(!path->dentry->d_op->d_manage); + ret = path->dentry->d_op->d_manage(path, false); + if (ret < 0) + break; + } + + /* Transit to a mounted filesystem. */ + if (managed & DCACHE_MOUNTED) { + struct vfsmount *mounted = lookup_mnt(path); + if (mounted) { + dput(path->dentry); + if (need_mntput) + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + need_mntput = true; + continue; + } + + /* Something is mounted on this dentry in another + * namespace and/or whatever was mounted there in this + * namespace got unmounted before lookup_mnt() could + * get it */ + } + + /* Handle an automount point */ + if (managed & DCACHE_NEED_AUTOMOUNT) { + ret = follow_automount(path, nd, &need_mntput); + if (ret < 0) + break; + continue; + } + + /* We didn't change the current path point */ + break; + } + + if (need_mntput && path->mnt == mnt) + mntput(path->mnt); + if (ret == -EISDIR || !ret) + ret = 1; + if (need_mntput) + nd->flags |= LOOKUP_JUMPED; + if (unlikely(ret < 0)) + path_put_conditional(path, nd); + return ret; +} + +int follow_down_one(struct path *path) +{ + struct vfsmount *mounted; + + mounted = lookup_mnt(path); + if (mounted) { + dput(path->dentry); + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + return 1; + } + return 0; +} +EXPORT_SYMBOL(follow_down_one); + +static inline int managed_dentry_rcu(const struct path *path) +{ + return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ? + path->dentry->d_op->d_manage(path, true) : 0; +} + +/* + * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if + * we meet a managed dentry that would need blocking. + */ +static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, + struct inode **inode, unsigned *seqp) +{ + for (;;) { + struct mount *mounted; + /* + * Don't forget we might have a non-mountpoint managed dentry + * that wants to block transit. + */ + switch (managed_dentry_rcu(path)) { + case -ECHILD: + default: + return false; + case -EISDIR: + return true; + case 0: + break; + } + + if (!d_mountpoint(path->dentry)) + return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); + + mounted = __lookup_mnt(path->mnt, path->dentry); + if (!mounted) + break; + path->mnt = &mounted->mnt; + path->dentry = mounted->mnt.mnt_root; + nd->flags |= LOOKUP_JUMPED; + *seqp = read_seqcount_begin(&path->dentry->d_seq); + /* + * Update the inode too. We don't need to re-check the + * dentry sequence number here after this d_inode read, + * because a mount-point is always pinned. + */ + *inode = path->dentry->d_inode; + } + return !read_seqretry(&mount_lock, nd->m_seq) && + !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); +} + +static int follow_dotdot_rcu(struct nameidata *nd) +{ + struct inode *inode = nd->inode; + + while (1) { + if (path_equal(&nd->path, &nd->root)) + break; + if (nd->path.dentry != nd->path.mnt->mnt_root) { + struct dentry *old = nd->path.dentry; + struct dentry *parent = old->d_parent; + unsigned seq; + + inode = parent->d_inode; + seq = read_seqcount_begin(&parent->d_seq); + if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq))) + return -ECHILD; + nd->path.dentry = parent; + nd->seq = seq; + if (unlikely(!path_connected(&nd->path))) + return -ECHILD; + break; + } else { + struct mount *mnt = real_mount(nd->path.mnt); + struct mount *mparent = mnt->mnt_parent; + struct dentry *mountpoint = mnt->mnt_mountpoint; + struct inode *inode2 = mountpoint->d_inode; + unsigned seq = read_seqcount_begin(&mountpoint->d_seq); + if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) + return -ECHILD; + if (&mparent->mnt == nd->path.mnt) + break; + /* we know that mountpoint was pinned */ + nd->path.dentry = mountpoint; + nd->path.mnt = &mparent->mnt; + inode = inode2; + nd->seq = seq; + } + } + while (unlikely(d_mountpoint(nd->path.dentry))) { + struct mount *mounted; + mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); + if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) + return -ECHILD; + if (!mounted) + break; + nd->path.mnt = &mounted->mnt; + nd->path.dentry = mounted->mnt.mnt_root; + inode = nd->path.dentry->d_inode; + nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); + } + nd->inode = inode; + return 0; +} + +/* + * Follow down to the covering mount currently visible to userspace. At each + * point, the filesystem owning that dentry may be queried as to whether the + * caller is permitted to proceed or not. + */ +int follow_down(struct path *path) +{ + unsigned managed; + int ret; + + while (managed = READ_ONCE(path->dentry->d_flags), + unlikely(managed & DCACHE_MANAGED_DENTRY)) { + /* Allow the filesystem to manage the transit without i_mutex + * being held. + * + * We indicate to the filesystem if someone is trying to mount + * something here. This gives autofs the chance to deny anyone + * other than its daemon the right to mount on its + * superstructure. + * + * The filesystem may sleep at this point. + */ + if (managed & DCACHE_MANAGE_TRANSIT) { + BUG_ON(!path->dentry->d_op); + BUG_ON(!path->dentry->d_op->d_manage); + ret = path->dentry->d_op->d_manage(path, false); + if (ret < 0) + return ret == -EISDIR ? 0 : ret; + } + + /* Transit to a mounted filesystem. */ + if (managed & DCACHE_MOUNTED) { + struct vfsmount *mounted = lookup_mnt(path); + if (!mounted) + break; + dput(path->dentry); + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + continue; + } + + /* Don't handle automount points here */ + break; + } + return 0; +} +EXPORT_SYMBOL(follow_down); + +/* + * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() + */ +static void follow_mount(struct path *path) +{ + while (d_mountpoint(path->dentry)) { + struct vfsmount *mounted = lookup_mnt(path); + if (!mounted) + break; + dput(path->dentry); + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + } +} + +static int path_parent_directory(struct path *path) +{ + struct dentry *old = path->dentry; + /* rare case of legitimate dget_parent()... */ + path->dentry = dget_parent(path->dentry); + dput(old); + if (unlikely(!path_connected(path))) + return -ENOENT; + return 0; +} + +static int follow_dotdot(struct nameidata *nd) +{ + while(1) { + if (path_equal(&nd->path, &nd->root)) + break; + if (nd->path.dentry != nd->path.mnt->mnt_root) { + int ret = path_parent_directory(&nd->path); + if (ret) + return ret; + break; + } + if (!follow_up(&nd->path)) + break; + } + follow_mount(&nd->path); + nd->inode = nd->path.dentry->d_inode; + return 0; +} + +/* + * This looks up the name in dcache and possibly revalidates the found dentry. + * NULL is returned if the dentry does not exist in the cache. + */ +static struct dentry *lookup_dcache(const struct qstr *name, + struct dentry *dir, + unsigned int flags) +{ + struct dentry *dentry = d_lookup(dir, name); + if (dentry) { + int error = d_revalidate(dentry, flags); + if (unlikely(error <= 0)) { + if (!error) + d_invalidate(dentry); + dput(dentry); + return ERR_PTR(error); + } + } + return dentry; +} + +/* + * Parent directory has inode locked exclusive. This is one + * and only case when ->lookup() gets called on non in-lookup + * dentries - as the matter of fact, this only gets called + * when directory is guaranteed to have no in-lookup children + * at all. + */ +static struct dentry *__lookup_hash(const struct qstr *name, + struct dentry *base, unsigned int flags) +{ + struct dentry *dentry = lookup_dcache(name, base, flags); + struct dentry *old; + struct inode *dir = base->d_inode; + + if (dentry) + return dentry; + + /* Don't create child dentry for a dead directory. */ + if (unlikely(IS_DEADDIR(dir))) + return ERR_PTR(-ENOENT); + + dentry = d_alloc(base, name); + if (unlikely(!dentry)) + return ERR_PTR(-ENOMEM); + + old = dir->i_op->lookup(dir, dentry, flags); + if (unlikely(old)) { + dput(dentry); + dentry = old; + } + return dentry; +} + +static int lookup_fast(struct nameidata *nd, + struct path *path, struct inode **inode, + unsigned *seqp) +{ + struct vfsmount *mnt = nd->path.mnt; + struct dentry *dentry, *parent = nd->path.dentry; + int status = 1; + int err; + + /* + * Rename seqlock is not required here because in the off chance + * of a false negative due to a concurrent rename, the caller is + * going to fall back to non-racy lookup. + */ + if (nd->flags & LOOKUP_RCU) { + unsigned seq; + bool negative; + dentry = __d_lookup_rcu(parent, &nd->last, &seq); + if (unlikely(!dentry)) { + if (unlazy_walk(nd)) + return -ECHILD; + return 0; + } + + /* + * This sequence count validates that the inode matches + * the dentry name information from lookup. + */ + *inode = d_backing_inode(dentry); + negative = d_is_negative(dentry); + if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) + return -ECHILD; + + /* + * This sequence count validates that the parent had no + * changes while we did the lookup of the dentry above. + * + * The memory barrier in read_seqcount_begin of child is + * enough, we can use __read_seqcount_retry here. + */ + if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq))) + return -ECHILD; + + *seqp = seq; + status = d_revalidate(dentry, nd->flags); + if (likely(status > 0)) { + /* + * Note: do negative dentry check after revalidation in + * case that drops it. + */ + if (unlikely(negative)) + return -ENOENT; + path->mnt = mnt; + path->dentry = dentry; + if (likely(__follow_mount_rcu(nd, path, inode, seqp))) + return 1; + } + if (unlazy_child(nd, dentry, seq)) + return -ECHILD; + if (unlikely(status == -ECHILD)) + /* we'd been told to redo it in non-rcu mode */ + status = d_revalidate(dentry, nd->flags); + } else { + dentry = __d_lookup(parent, &nd->last); + if (unlikely(!dentry)) + return 0; + status = d_revalidate(dentry, nd->flags); + } + if (unlikely(status <= 0)) { + if (!status) + d_invalidate(dentry); + dput(dentry); + return status; + } + if (unlikely(d_is_negative(dentry))) { + dput(dentry); + return -ENOENT; + } + + path->mnt = mnt; + path->dentry = dentry; + err = follow_managed(path, nd); + if (likely(err > 0)) + *inode = d_backing_inode(path->dentry); + return err; +} + +/* Fast lookup failed, do it the slow way */ +static struct dentry *__lookup_slow(const struct qstr *name, + struct dentry *dir, + unsigned int flags) +{ + struct dentry *dentry, *old; + struct inode *inode = dir->d_inode; + DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); + + /* Don't go there if it's already dead */ + if (unlikely(IS_DEADDIR(inode))) + return ERR_PTR(-ENOENT); +again: + dentry = d_alloc_parallel(dir, name, &wq); + if (IS_ERR(dentry)) + return dentry; + if (unlikely(!d_in_lookup(dentry))) { + if (!(flags & LOOKUP_NO_REVAL)) { + int error = d_revalidate(dentry, flags); + if (unlikely(error <= 0)) { + if (!error) { + d_invalidate(dentry); + dput(dentry); + goto again; + } + dput(dentry); + dentry = ERR_PTR(error); + } + } + } else { + old = inode->i_op->lookup(inode, dentry, flags); + d_lookup_done(dentry); + if (unlikely(old)) { + dput(dentry); + dentry = old; + } + } + return dentry; +} + +static struct dentry *lookup_slow(const struct qstr *name, + struct dentry *dir, + unsigned int flags) +{ + struct inode *inode = dir->d_inode; + struct dentry *res; + inode_lock_shared(inode); + res = __lookup_slow(name, dir, flags); + inode_unlock_shared(inode); + return res; +} + +static inline int may_lookup(struct nameidata *nd) +{ + if (nd->flags & LOOKUP_RCU) { + int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); + if (err != -ECHILD) + return err; + if (unlazy_walk(nd)) + return -ECHILD; + } + return inode_permission(nd->inode, MAY_EXEC); +} + +static inline int handle_dots(struct nameidata *nd, int type) +{ + if (type == LAST_DOTDOT) { + if (!nd->root.mnt) + set_root(nd); + if (nd->flags & LOOKUP_RCU) { + return follow_dotdot_rcu(nd); + } else + return follow_dotdot(nd); + } + return 0; +} + +static int pick_link(struct nameidata *nd, struct path *link, + struct inode *inode, unsigned seq) +{ + int error; + struct saved *last; + if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) { + path_to_nameidata(link, nd); + return -ELOOP; + } + if (!(nd->flags & LOOKUP_RCU)) { + if (link->mnt == nd->path.mnt) + mntget(link->mnt); + } + error = nd_alloc_stack(nd); + if (unlikely(error)) { + if (error == -ECHILD) { + if (unlikely(!legitimize_path(nd, link, seq))) { + drop_links(nd); + nd->depth = 0; + nd->flags &= ~LOOKUP_RCU; + nd->path.mnt = NULL; + nd->path.dentry = NULL; + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; + rcu_read_unlock(); + } else if (likely(unlazy_walk(nd)) == 0) + error = nd_alloc_stack(nd); + } + if (error) { + path_put(link); + return error; + } + } + + last = nd->stack + nd->depth++; + last->link = *link; + clear_delayed_call(&last->done); + nd->link_inode = inode; + last->seq = seq; + return 1; +} + +enum {WALK_FOLLOW = 1, WALK_MORE = 2}; + +/* + * Do we need to follow links? We _really_ want to be able + * to do this check without having to look at inode->i_op, + * so we keep a cache of "no, this doesn't need follow_link" + * for the common case. + */ +static inline int step_into(struct nameidata *nd, struct path *path, + int flags, struct inode *inode, unsigned seq) +{ + if (!(flags & WALK_MORE) && nd->depth) + put_link(nd); + if (likely(!d_is_symlink(path->dentry)) || + !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) { + /* not a symlink or should not follow */ + path_to_nameidata(path, nd); + nd->inode = inode; + nd->seq = seq; + return 0; + } + /* make sure that d_is_symlink above matches inode */ + if (nd->flags & LOOKUP_RCU) { + if (read_seqcount_retry(&path->dentry->d_seq, seq)) + return -ECHILD; + } + return pick_link(nd, path, inode, seq); +} + +static int walk_component(struct nameidata *nd, int flags) +{ + struct path path; + struct inode *inode; + unsigned seq; + int err; + /* + * "." and ".." are special - ".." especially so because it has + * to be able to know about the current root directory and + * parent relationships. + */ + if (unlikely(nd->last_type != LAST_NORM)) { + err = handle_dots(nd, nd->last_type); + if (!(flags & WALK_MORE) && nd->depth) + put_link(nd); + return err; + } + err = lookup_fast(nd, &path, &inode, &seq); + if (unlikely(err <= 0)) { + if (err < 0) + return err; + path.dentry = lookup_slow(&nd->last, nd->path.dentry, + nd->flags); + if (IS_ERR(path.dentry)) + return PTR_ERR(path.dentry); + + path.mnt = nd->path.mnt; + err = follow_managed(&path, nd); + if (unlikely(err < 0)) + return err; + + if (unlikely(d_is_negative(path.dentry))) { + path_to_nameidata(&path, nd); + return -ENOENT; + } + + seq = 0; /* we are already out of RCU mode */ + inode = d_backing_inode(path.dentry); + } + + return step_into(nd, &path, flags, inode, seq); +} + +/* + * We can do the critical dentry name comparison and hashing + * operations one word at a time, but we are limited to: + * + * - Architectures with fast unaligned word accesses. We could + * do a "get_unaligned()" if this helps and is sufficiently + * fast. + * + * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we + * do not trap on the (extremely unlikely) case of a page + * crossing operation. + * + * - Furthermore, we need an efficient 64-bit compile for the + * 64-bit case in order to generate the "number of bytes in + * the final mask". Again, that could be replaced with a + * efficient population count instruction or similar. + */ +#ifdef CONFIG_DCACHE_WORD_ACCESS + +#include <asm/word-at-a-time.h> + +#ifdef HASH_MIX + +/* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */ + +#elif defined(CONFIG_64BIT) +/* + * Register pressure in the mixing function is an issue, particularly + * on 32-bit x86, but almost any function requires one state value and + * one temporary. Instead, use a function designed for two state values + * and no temporaries. + * + * This function cannot create a collision in only two iterations, so + * we have two iterations to achieve avalanche. In those two iterations, + * we have six layers of mixing, which is enough to spread one bit's + * influence out to 2^6 = 64 state bits. + * + * Rotate constants are scored by considering either 64 one-bit input + * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the + * probability of that delta causing a change to each of the 128 output + * bits, using a sample of random initial states. + * + * The Shannon entropy of the computed probabilities is then summed + * to produce a score. Ideally, any input change has a 50% chance of + * toggling any given output bit. + * + * Mixing scores (in bits) for (12,45): + * Input delta: 1-bit 2-bit + * 1 round: 713.3 42542.6 + * 2 rounds: 2753.7 140389.8 + * 3 rounds: 5954.1 233458.2 + * 4 rounds: 7862.6 256672.2 + * Perfect: 8192 258048 + * (64*128) (64*63/2 * 128) + */ +#define HASH_MIX(x, y, a) \ + ( x ^= (a), \ + y ^= x, x = rol64(x,12),\ + x += y, y = rol64(y,45),\ + y *= 9 ) + +/* + * Fold two longs into one 32-bit hash value. This must be fast, but + * latency isn't quite as critical, as there is a fair bit of additional + * work done before the hash value is used. + */ +static inline unsigned int fold_hash(unsigned long x, unsigned long y) +{ + y ^= x * GOLDEN_RATIO_64; + y *= GOLDEN_RATIO_64; + return y >> 32; +} + +#else /* 32-bit case */ + +/* + * Mixing scores (in bits) for (7,20): + * Input delta: 1-bit 2-bit + * 1 round: 330.3 9201.6 + * 2 rounds: 1246.4 25475.4 + * 3 rounds: 1907.1 31295.1 + * 4 rounds: 2042.3 31718.6 + * Perfect: 2048 31744 + * (32*64) (32*31/2 * 64) + */ +#define HASH_MIX(x, y, a) \ + ( x ^= (a), \ + y ^= x, x = rol32(x, 7),\ + x += y, y = rol32(y,20),\ + y *= 9 ) + +static inline unsigned int fold_hash(unsigned long x, unsigned long y) +{ + /* Use arch-optimized multiply if one exists */ + return __hash_32(y ^ __hash_32(x)); +} + +#endif + +/* + * Return the hash of a string of known length. This is carfully + * designed to match hash_name(), which is the more critical function. + * In particular, we must end by hashing a final word containing 0..7 + * payload bytes, to match the way that hash_name() iterates until it + * finds the delimiter after the name. + */ +unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) +{ + unsigned long a, x = 0, y = (unsigned long)salt; + + for (;;) { + if (!len) + goto done; + a = load_unaligned_zeropad(name); + if (len < sizeof(unsigned long)) + break; + HASH_MIX(x, y, a); + name += sizeof(unsigned long); + len -= sizeof(unsigned long); + } + x ^= a & bytemask_from_count(len); +done: + return fold_hash(x, y); +} +EXPORT_SYMBOL(full_name_hash); + +/* Return the "hash_len" (hash and length) of a null-terminated string */ +u64 hashlen_string(const void *salt, const char *name) +{ + unsigned long a = 0, x = 0, y = (unsigned long)salt; + unsigned long adata, mask, len; + const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; + + len = 0; + goto inside; + + do { + HASH_MIX(x, y, a); + len += sizeof(unsigned long); +inside: + a = load_unaligned_zeropad(name+len); + } while (!has_zero(a, &adata, &constants)); + + adata = prep_zero_mask(a, adata, &constants); + mask = create_zero_mask(adata); + x ^= a & zero_bytemask(mask); + + return hashlen_create(fold_hash(x, y), len + find_zero(mask)); +} +EXPORT_SYMBOL(hashlen_string); + +/* + * Calculate the length and hash of the path component, and + * return the "hash_len" as the result. + */ +static inline u64 hash_name(const void *salt, const char *name) +{ + unsigned long a = 0, b, x = 0, y = (unsigned long)salt; + unsigned long adata, bdata, mask, len; + const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; + + len = 0; + goto inside; + + do { + HASH_MIX(x, y, a); + len += sizeof(unsigned long); +inside: + a = load_unaligned_zeropad(name+len); + b = a ^ REPEAT_BYTE('/'); + } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); + + adata = prep_zero_mask(a, adata, &constants); + bdata = prep_zero_mask(b, bdata, &constants); + mask = create_zero_mask(adata | bdata); + x ^= a & zero_bytemask(mask); + + return hashlen_create(fold_hash(x, y), len + find_zero(mask)); +} + +#else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */ + +/* Return the hash of a string of known length */ +unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) +{ + unsigned long hash = init_name_hash(salt); + while (len--) + hash = partial_name_hash((unsigned char)*name++, hash); + return end_name_hash(hash); +} +EXPORT_SYMBOL(full_name_hash); + +/* Return the "hash_len" (hash and length) of a null-terminated string */ +u64 hashlen_string(const void *salt, const char *name) +{ + unsigned long hash = init_name_hash(salt); + unsigned long len = 0, c; + + c = (unsigned char)*name; + while (c) { + len++; + hash = partial_name_hash(c, hash); + c = (unsigned char)name[len]; + } + return hashlen_create(end_name_hash(hash), len); +} +EXPORT_SYMBOL(hashlen_string); + +/* + * We know there's a real path component here of at least + * one character. + */ +static inline u64 hash_name(const void *salt, const char *name) +{ + unsigned long hash = init_name_hash(salt); + unsigned long len = 0, c; + + c = (unsigned char)*name; + do { + len++; + hash = partial_name_hash(c, hash); + c = (unsigned char)name[len]; + } while (c && c != '/'); + return hashlen_create(end_name_hash(hash), len); +} + +#endif + +/* + * Name resolution. + * This is the basic name resolution function, turning a pathname into + * the final dentry. We expect 'base' to be positive and a directory. + * + * Returns 0 and nd will have valid dentry and mnt on success. + * Returns error and drops reference to input namei data on failure. + */ +static int link_path_walk(const char *name, struct nameidata *nd) +{ + int err; + + if (IS_ERR(name)) + return PTR_ERR(name); + while (*name=='/') + name++; + if (!*name) + return 0; + + /* At this point we know we have a real path component. */ + for(;;) { + u64 hash_len; + int type; + + err = may_lookup(nd); + if (err) + return err; + + hash_len = hash_name(nd->path.dentry, name); + + type = LAST_NORM; + if (name[0] == '.') switch (hashlen_len(hash_len)) { + case 2: + if (name[1] == '.') { + type = LAST_DOTDOT; + nd->flags |= LOOKUP_JUMPED; + } + break; + case 1: + type = LAST_DOT; + } + if (likely(type == LAST_NORM)) { + struct dentry *parent = nd->path.dentry; + nd->flags &= ~LOOKUP_JUMPED; + if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { + struct qstr this = { { .hash_len = hash_len }, .name = name }; + err = parent->d_op->d_hash(parent, &this); + if (err < 0) + return err; + hash_len = this.hash_len; + name = this.name; + } + } + + nd->last.hash_len = hash_len; + nd->last.name = name; + nd->last_type = type; + + name += hashlen_len(hash_len); + if (!*name) + goto OK; + /* + * If it wasn't NUL, we know it was '/'. Skip that + * slash, and continue until no more slashes. + */ + do { + name++; + } while (unlikely(*name == '/')); + if (unlikely(!*name)) { +OK: + /* pathname body, done */ + if (!nd->depth) + return 0; + name = nd->stack[nd->depth - 1].name; + /* trailing symlink, done */ + if (!name) + return 0; + /* last component of nested symlink */ + err = walk_component(nd, WALK_FOLLOW); + } else { + /* not the last component */ + err = walk_component(nd, WALK_FOLLOW | WALK_MORE); + } + if (err < 0) + return err; + + if (err) { + const char *s = get_link(nd); + + if (IS_ERR(s)) + return PTR_ERR(s); + err = 0; + if (unlikely(!s)) { + /* jumped */ + put_link(nd); + } else { + nd->stack[nd->depth - 1].name = name; + name = s; + continue; + } + } + if (unlikely(!d_can_lookup(nd->path.dentry))) { + if (nd->flags & LOOKUP_RCU) { + if (unlazy_walk(nd)) + return -ECHILD; + } + return -ENOTDIR; + } + } +} + +/* must be paired with terminate_walk() */ +static const char *path_init(struct nameidata *nd, unsigned flags) +{ + const char *s = nd->name->name; + + if (!*s) + flags &= ~LOOKUP_RCU; + if (flags & LOOKUP_RCU) + rcu_read_lock(); + + nd->last_type = LAST_ROOT; /* if there are only slashes... */ + nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT; + nd->depth = 0; + if (flags & LOOKUP_ROOT) { + struct dentry *root = nd->root.dentry; + struct inode *inode = root->d_inode; + if (*s && unlikely(!d_can_lookup(root))) + return ERR_PTR(-ENOTDIR); + nd->path = nd->root; + nd->inode = inode; + if (flags & LOOKUP_RCU) { + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); + nd->root_seq = nd->seq; + nd->m_seq = read_seqbegin(&mount_lock); + } else { + path_get(&nd->path); + } + return s; + } + + nd->root.mnt = NULL; + nd->path.mnt = NULL; + nd->path.dentry = NULL; + + nd->m_seq = read_seqbegin(&mount_lock); + if (*s == '/') { + set_root(nd); + if (likely(!nd_jump_root(nd))) + return s; + return ERR_PTR(-ECHILD); + } else if (nd->dfd == AT_FDCWD) { + if (flags & LOOKUP_RCU) { + struct fs_struct *fs = current->fs; + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + nd->path = fs->pwd; + nd->inode = nd->path.dentry->d_inode; + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); + } while (read_seqcount_retry(&fs->seq, seq)); + } else { + get_fs_pwd(current->fs, &nd->path); + nd->inode = nd->path.dentry->d_inode; + } + return s; + } else { + /* Caller must check execute permissions on the starting path component */ + struct fd f = fdget_raw(nd->dfd); + struct dentry *dentry; + + if (!f.file) + return ERR_PTR(-EBADF); + + dentry = f.file->f_path.dentry; + + if (*s && unlikely(!d_can_lookup(dentry))) { + fdput(f); + return ERR_PTR(-ENOTDIR); + } + + nd->path = f.file->f_path; + if (flags & LOOKUP_RCU) { + nd->inode = nd->path.dentry->d_inode; + nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); + } else { + path_get(&nd->path); + nd->inode = nd->path.dentry->d_inode; + } + fdput(f); + return s; + } +} + +static const char *trailing_symlink(struct nameidata *nd) +{ + const char *s; + int error = may_follow_link(nd); + if (unlikely(error)) + return ERR_PTR(error); + nd->flags |= LOOKUP_PARENT; + nd->stack[0].name = NULL; + s = get_link(nd); + return s ? s : ""; +} + +static inline int lookup_last(struct nameidata *nd) +{ + if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) + nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; + + nd->flags &= ~LOOKUP_PARENT; + return walk_component(nd, 0); +} + +static int handle_lookup_down(struct nameidata *nd) +{ + struct path path = nd->path; + struct inode *inode = nd->inode; + unsigned seq = nd->seq; + int err; + + if (nd->flags & LOOKUP_RCU) { + /* + * don't bother with unlazy_walk on failure - we are + * at the very beginning of walk, so we lose nothing + * if we simply redo everything in non-RCU mode + */ + if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq))) + return -ECHILD; + } else { + dget(path.dentry); + err = follow_managed(&path, nd); + if (unlikely(err < 0)) + return err; + inode = d_backing_inode(path.dentry); + seq = 0; + } + path_to_nameidata(&path, nd); + nd->inode = inode; + nd->seq = seq; + return 0; +} + +/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ +static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path) +{ + const char *s = path_init(nd, flags); + int err; + + if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) { + err = handle_lookup_down(nd); + if (unlikely(err < 0)) + s = ERR_PTR(err); + } + + while (!(err = link_path_walk(s, nd)) + && ((err = lookup_last(nd)) > 0)) { + s = trailing_symlink(nd); + } + if (!err) + err = complete_walk(nd); + + if (!err && nd->flags & LOOKUP_DIRECTORY) + if (!d_can_lookup(nd->path.dentry)) + err = -ENOTDIR; + if (!err) { + *path = nd->path; + nd->path.mnt = NULL; + nd->path.dentry = NULL; + } + terminate_walk(nd); + return err; +} + +static int filename_lookup(int dfd, struct filename *name, unsigned flags, + struct path *path, struct path *root) +{ + int retval; + struct nameidata nd; + if (IS_ERR(name)) + return PTR_ERR(name); + if (unlikely(root)) { + nd.root = *root; + flags |= LOOKUP_ROOT; + } + set_nameidata(&nd, dfd, name); + retval = path_lookupat(&nd, flags | LOOKUP_RCU, path); + if (unlikely(retval == -ECHILD)) + retval = path_lookupat(&nd, flags, path); + if (unlikely(retval == -ESTALE)) + retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path); + + if (likely(!retval)) + audit_inode(name, path->dentry, flags & LOOKUP_PARENT); + restore_nameidata(); + putname(name); + return retval; +} + +/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ +static int path_parentat(struct nameidata *nd, unsigned flags, + struct path *parent) +{ + const char *s = path_init(nd, flags); + int err = link_path_walk(s, nd); + if (!err) + err = complete_walk(nd); + if (!err) { + *parent = nd->path; + nd->path.mnt = NULL; + nd->path.dentry = NULL; + } + terminate_walk(nd); + return err; +} + +static struct filename *filename_parentat(int dfd, struct filename *name, + unsigned int flags, struct path *parent, + struct qstr *last, int *type) +{ + int retval; + struct nameidata nd; + + if (IS_ERR(name)) + return name; + set_nameidata(&nd, dfd, name); + retval = path_parentat(&nd, flags | LOOKUP_RCU, parent); + if (unlikely(retval == -ECHILD)) + retval = path_parentat(&nd, flags, parent); + if (unlikely(retval == -ESTALE)) + retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent); + if (likely(!retval)) { + *last = nd.last; + *type = nd.last_type; + audit_inode(name, parent->dentry, LOOKUP_PARENT); + } else { + putname(name); + name = ERR_PTR(retval); + } + restore_nameidata(); + return name; +} + +/* does lookup, returns the object with parent locked */ +struct dentry *kern_path_locked(const char *name, struct path *path) +{ + struct filename *filename; + struct dentry *d; + struct qstr last; + int type; + + filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path, + &last, &type); + if (IS_ERR(filename)) + return ERR_CAST(filename); + if (unlikely(type != LAST_NORM)) { + path_put(path); + putname(filename); + return ERR_PTR(-EINVAL); + } + inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); + d = __lookup_hash(&last, path->dentry, 0); + if (IS_ERR(d)) { + inode_unlock(path->dentry->d_inode); + path_put(path); + } + putname(filename); + return d; +} + +int kern_path(const char *name, unsigned int flags, struct path *path) +{ + return filename_lookup(AT_FDCWD, getname_kernel(name), + flags, path, NULL); +} +EXPORT_SYMBOL(kern_path); + +/** + * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair + * @dentry: pointer to dentry of the base directory + * @mnt: pointer to vfs mount of the base directory + * @name: pointer to file name + * @flags: lookup flags + * @path: pointer to struct path to fill + */ +int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, + const char *name, unsigned int flags, + struct path *path) +{ + struct path root = {.mnt = mnt, .dentry = dentry}; + /* the first argument of filename_lookup() is ignored with root */ + return filename_lookup(AT_FDCWD, getname_kernel(name), + flags , path, &root); +} +EXPORT_SYMBOL(vfs_path_lookup); + +static int lookup_one_len_common(const char *name, struct dentry *base, + int len, struct qstr *this) +{ + this->name = name; + this->len = len; + this->hash = full_name_hash(base, name, len); + if (!len) + return -EACCES; + + if (unlikely(name[0] == '.')) { + if (len < 2 || (len == 2 && name[1] == '.')) + return -EACCES; + } + + while (len--) { + unsigned int c = *(const unsigned char *)name++; + if (c == '/' || c == '\0') + return -EACCES; + } + /* + * See if the low-level filesystem might want + * to use its own hash.. + */ + if (base->d_flags & DCACHE_OP_HASH) { + int err = base->d_op->d_hash(base, this); + if (err < 0) + return err; + } + + return inode_permission(base->d_inode, MAY_EXEC); +} + +/** + * try_lookup_one_len - filesystem helper to lookup single pathname component + * @name: pathname component to lookup + * @base: base directory to lookup from + * @len: maximum length @len should be interpreted to + * + * Look up a dentry by name in the dcache, returning NULL if it does not + * currently exist. The function does not try to create a dentry. + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. + * + * The caller must hold base->i_mutex. + */ +struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len) +{ + struct qstr this; + int err; + + WARN_ON_ONCE(!inode_is_locked(base->d_inode)); + + err = lookup_one_len_common(name, base, len, &this); + if (err) + return ERR_PTR(err); + + return lookup_dcache(&this, base, 0); +} +EXPORT_SYMBOL(try_lookup_one_len); + +/** + * lookup_one_len - filesystem helper to lookup single pathname component + * @name: pathname component to lookup + * @base: base directory to lookup from + * @len: maximum length @len should be interpreted to + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. + * + * The caller must hold base->i_mutex. + */ +struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) +{ + struct dentry *dentry; + struct qstr this; + int err; + + WARN_ON_ONCE(!inode_is_locked(base->d_inode)); + + err = lookup_one_len_common(name, base, len, &this); + if (err) + return ERR_PTR(err); + + dentry = lookup_dcache(&this, base, 0); + return dentry ? dentry : __lookup_slow(&this, base, 0); +} +EXPORT_SYMBOL(lookup_one_len); + +/** + * lookup_one_len_unlocked - filesystem helper to lookup single pathname component + * @name: pathname component to lookup + * @base: base directory to lookup from + * @len: maximum length @len should be interpreted to + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. + * + * Unlike lookup_one_len, it should be called without the parent + * i_mutex held, and will take the i_mutex itself if necessary. + */ +struct dentry *lookup_one_len_unlocked(const char *name, + struct dentry *base, int len) +{ + struct qstr this; + int err; + struct dentry *ret; + + err = lookup_one_len_common(name, base, len, &this); + if (err) + return ERR_PTR(err); + + ret = lookup_dcache(&this, base, 0); + if (!ret) + ret = lookup_slow(&this, base, 0); + return ret; +} +EXPORT_SYMBOL(lookup_one_len_unlocked); + +#ifdef CONFIG_UNIX98_PTYS +int path_pts(struct path *path) +{ + /* Find something mounted on "pts" in the same directory as + * the input path. + */ + struct dentry *child, *parent; + struct qstr this; + int ret; + + ret = path_parent_directory(path); + if (ret) + return ret; + + parent = path->dentry; + this.name = "pts"; + this.len = 3; + child = d_hash_and_lookup(parent, &this); + if (!child) + return -ENOENT; + + path->dentry = child; + dput(parent); + follow_mount(path); + return 0; +} +#endif + +int user_path_at_empty(int dfd, const char __user *name, unsigned flags, + struct path *path, int *empty) +{ + return filename_lookup(dfd, getname_flags(name, flags, empty), + flags, path, NULL); +} +EXPORT_SYMBOL(user_path_at_empty); + +/** + * mountpoint_last - look up last component for umount + * @nd: pathwalk nameidata - currently pointing at parent directory of "last" + * + * This is a special lookup_last function just for umount. In this case, we + * need to resolve the path without doing any revalidation. + * + * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since + * mountpoints are always pinned in the dcache, their ancestors are too. Thus, + * in almost all cases, this lookup will be served out of the dcache. The only + * cases where it won't are if nd->last refers to a symlink or the path is + * bogus and it doesn't exist. + * + * Returns: + * -error: if there was an error during lookup. This includes -ENOENT if the + * lookup found a negative dentry. + * + * 0: if we successfully resolved nd->last and found it to not to be a + * symlink that needs to be followed. + * + * 1: if we successfully resolved nd->last and found it to be a symlink + * that needs to be followed. + */ +static int +mountpoint_last(struct nameidata *nd) +{ + int error = 0; + struct dentry *dir = nd->path.dentry; + struct path path; + + /* If we're in rcuwalk, drop out of it to handle last component */ + if (nd->flags & LOOKUP_RCU) { + if (unlazy_walk(nd)) + return -ECHILD; + } + + nd->flags &= ~LOOKUP_PARENT; + + if (unlikely(nd->last_type != LAST_NORM)) { + error = handle_dots(nd, nd->last_type); + if (error) + return error; + path.dentry = dget(nd->path.dentry); + } else { + path.dentry = d_lookup(dir, &nd->last); + if (!path.dentry) { + /* + * No cached dentry. Mounted dentries are pinned in the + * cache, so that means that this dentry is probably + * a symlink or the path doesn't actually point + * to a mounted dentry. + */ + path.dentry = lookup_slow(&nd->last, dir, + nd->flags | LOOKUP_NO_REVAL); + if (IS_ERR(path.dentry)) + return PTR_ERR(path.dentry); + } + } + if (d_is_negative(path.dentry)) { + dput(path.dentry); + return -ENOENT; + } + path.mnt = nd->path.mnt; + return step_into(nd, &path, 0, d_backing_inode(path.dentry), 0); +} + +/** + * path_mountpoint - look up a path to be umounted + * @nd: lookup context + * @flags: lookup flags + * @path: pointer to container for result + * + * Look up the given name, but don't attempt to revalidate the last component. + * Returns 0 and "path" will be valid on success; Returns error otherwise. + */ +static int +path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path) +{ + const char *s = path_init(nd, flags); + int err; + + while (!(err = link_path_walk(s, nd)) && + (err = mountpoint_last(nd)) > 0) { + s = trailing_symlink(nd); + } + if (!err) { + *path = nd->path; + nd->path.mnt = NULL; + nd->path.dentry = NULL; + follow_mount(path); + } + terminate_walk(nd); + return err; +} + +static int +filename_mountpoint(int dfd, struct filename *name, struct path *path, + unsigned int flags) +{ + struct nameidata nd; + int error; + if (IS_ERR(name)) + return PTR_ERR(name); + set_nameidata(&nd, dfd, name); + error = path_mountpoint(&nd, flags | LOOKUP_RCU, path); + if (unlikely(error == -ECHILD)) + error = path_mountpoint(&nd, flags, path); + if (unlikely(error == -ESTALE)) + error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path); + if (likely(!error)) + audit_inode(name, path->dentry, 0); + restore_nameidata(); + putname(name); + return error; +} + +/** + * user_path_mountpoint_at - lookup a path from userland in order to umount it + * @dfd: directory file descriptor + * @name: pathname from userland + * @flags: lookup flags + * @path: pointer to container to hold result + * + * A umount is a special case for path walking. We're not actually interested + * in the inode in this situation, and ESTALE errors can be a problem. We + * simply want track down the dentry and vfsmount attached at the mountpoint + * and avoid revalidating the last component. + * + * Returns 0 and populates "path" on success. + */ +int +user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags, + struct path *path) +{ + return filename_mountpoint(dfd, getname(name), path, flags); +} + +int +kern_path_mountpoint(int dfd, const char *name, struct path *path, + unsigned int flags) +{ + return filename_mountpoint(dfd, getname_kernel(name), path, flags); +} +EXPORT_SYMBOL(kern_path_mountpoint); + +int __check_sticky(struct inode *dir, struct inode *inode) +{ + kuid_t fsuid = current_fsuid(); + + if (uid_eq(inode->i_uid, fsuid)) + return 0; + if (uid_eq(dir->i_uid, fsuid)) + return 0; + return !capable_wrt_inode_uidgid(inode, CAP_FOWNER); +} +EXPORT_SYMBOL(__check_sticky); + +/* + * Check whether we can remove a link victim from directory dir, check + * whether the type of victim is right. + * 1. We can't do it if dir is read-only (done in permission()) + * 2. We should have write and exec permissions on dir + * 3. We can't remove anything from append-only dir + * 4. We can't do anything with immutable dir (done in permission()) + * 5. If the sticky bit on dir is set we should either + * a. be owner of dir, or + * b. be owner of victim, or + * c. have CAP_FOWNER capability + * 6. If the victim is append-only or immutable we can't do antyhing with + * links pointing to it. + * 7. If the victim has an unknown uid or gid we can't change the inode. + * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR. + * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR. + * 10. We can't remove a root or mountpoint. + * 11. We don't allow removal of NFS sillyrenamed files; it's handled by + * nfs_async_unlink(). + */ +static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) +{ + struct inode *inode = d_backing_inode(victim); + int error; + + if (d_is_negative(victim)) + return -ENOENT; + BUG_ON(!inode); + + BUG_ON(victim->d_parent->d_inode != dir); + + /* Inode writeback is not safe when the uid or gid are invalid. */ + if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) + return -EOVERFLOW; + + audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); + + error = inode_permission(dir, MAY_WRITE | MAY_EXEC); + if (error) + return error; + if (IS_APPEND(dir)) + return -EPERM; + + if (check_sticky(dir, inode) || IS_APPEND(inode) || + IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode)) + return -EPERM; + if (isdir) { + if (!d_is_dir(victim)) + return -ENOTDIR; + if (IS_ROOT(victim)) + return -EBUSY; + } else if (d_is_dir(victim)) + return -EISDIR; + if (IS_DEADDIR(dir)) + return -ENOENT; + if (victim->d_flags & DCACHE_NFSFS_RENAMED) + return -EBUSY; + return 0; +} + +/* Check whether we can create an object with dentry child in directory + * dir. + * 1. We can't do it if child already exists (open has special treatment for + * this case, but since we are inlined it's OK) + * 2. We can't do it if dir is read-only (done in permission()) + * 3. We can't do it if the fs can't represent the fsuid or fsgid. + * 4. We should have write and exec permissions on dir + * 5. We can't do it if dir is immutable (done in permission()) + */ +static inline int may_create(struct inode *dir, struct dentry *child) +{ + struct user_namespace *s_user_ns; + audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); + if (child->d_inode) + return -EEXIST; + if (IS_DEADDIR(dir)) + return -ENOENT; + s_user_ns = dir->i_sb->s_user_ns; + if (!kuid_has_mapping(s_user_ns, current_fsuid()) || + !kgid_has_mapping(s_user_ns, current_fsgid())) + return -EOVERFLOW; + return inode_permission(dir, MAY_WRITE | MAY_EXEC); +} + +/* + * p1 and p2 should be directories on the same fs. + */ +struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) +{ + struct dentry *p; + + if (p1 == p2) { + inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); + return NULL; + } + + mutex_lock(&p1->d_sb->s_vfs_rename_mutex); + + p = d_ancestor(p2, p1); + if (p) { + inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); + inode_lock_nested(p1->d_inode, I_MUTEX_CHILD); + return p; + } + + p = d_ancestor(p1, p2); + if (p) { + inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); + inode_lock_nested(p2->d_inode, I_MUTEX_CHILD); + return p; + } + + inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); + inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2); + return NULL; +} +EXPORT_SYMBOL(lock_rename); + +void unlock_rename(struct dentry *p1, struct dentry *p2) +{ + inode_unlock(p1->d_inode); + if (p1 != p2) { + inode_unlock(p2->d_inode); + mutex_unlock(&p1->d_sb->s_vfs_rename_mutex); + } +} +EXPORT_SYMBOL(unlock_rename); + +int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, + bool want_excl) +{ + int error = may_create(dir, dentry); + if (error) + return error; + + if (!dir->i_op->create) + return -EACCES; /* shouldn't it be ENOSYS? */ + mode &= S_IALLUGO; + mode |= S_IFREG; + error = security_inode_create(dir, dentry, mode); + if (error) + return error; + error = dir->i_op->create(dir, dentry, mode, want_excl); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_create); + +int vfs_mkobj(struct dentry *dentry, umode_t mode, + int (*f)(struct dentry *, umode_t, void *), + void *arg) +{ + struct inode *dir = dentry->d_parent->d_inode; + int error = may_create(dir, dentry); + if (error) + return error; + + mode &= S_IALLUGO; + mode |= S_IFREG; + error = security_inode_create(dir, dentry, mode); + if (error) + return error; + error = f(dentry, mode, arg); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_mkobj); + +bool may_open_dev(const struct path *path) +{ + return !(path->mnt->mnt_flags & MNT_NODEV) && + !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV); +} + +static int may_open(const struct path *path, int acc_mode, int flag) +{ + struct dentry *dentry = path->dentry; + struct inode *inode = dentry->d_inode; + int error; + + if (!inode) + return -ENOENT; + + switch (inode->i_mode & S_IFMT) { + case S_IFLNK: + return -ELOOP; + case S_IFDIR: + if (acc_mode & MAY_WRITE) + return -EISDIR; + break; + case S_IFBLK: + case S_IFCHR: + if (!may_open_dev(path)) + return -EACCES; + /*FALLTHRU*/ + case S_IFIFO: + case S_IFSOCK: + flag &= ~O_TRUNC; + break; + } + + error = inode_permission(inode, MAY_OPEN | acc_mode); + if (error) + return error; + + /* + * An append-only file must be opened in append mode for writing. + */ + if (IS_APPEND(inode)) { + if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) + return -EPERM; + if (flag & O_TRUNC) + return -EPERM; + } + + /* O_NOATIME can only be set by the owner or superuser */ + if (flag & O_NOATIME && !inode_owner_or_capable(inode)) + return -EPERM; + + return 0; +} + +static int handle_truncate(struct file *filp) +{ + const struct path *path = &filp->f_path; + struct inode *inode = path->dentry->d_inode; + int error = get_write_access(inode); + if (error) + return error; + /* + * Refuse to truncate files with mandatory locks held on them. + */ + error = locks_verify_locked(filp); + if (!error) + error = security_path_truncate(path); + if (!error) { + error = do_truncate(path->dentry, 0, + ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, + filp); + } + put_write_access(inode); + return error; +} + +static inline int open_to_namei_flags(int flag) +{ + if ((flag & O_ACCMODE) == 3) + flag--; + return flag; +} + +static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode) +{ + struct user_namespace *s_user_ns; + int error = security_path_mknod(dir, dentry, mode, 0); + if (error) + return error; + + s_user_ns = dir->dentry->d_sb->s_user_ns; + if (!kuid_has_mapping(s_user_ns, current_fsuid()) || + !kgid_has_mapping(s_user_ns, current_fsgid())) + return -EOVERFLOW; + + error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); + if (error) + return error; + + return security_inode_create(dir->dentry->d_inode, dentry, mode); +} + +/* + * Attempt to atomically look up, create and open a file from a negative + * dentry. + * + * Returns 0 if successful. The file will have been created and attached to + * @file by the filesystem calling finish_open(). + * + * If the file was looked up only or didn't need creating, FMODE_OPENED won't + * be set. The caller will need to perform the open themselves. @path will + * have been updated to point to the new dentry. This may be negative. + * + * Returns an error code otherwise. + */ +static int atomic_open(struct nameidata *nd, struct dentry *dentry, + struct path *path, struct file *file, + const struct open_flags *op, + int open_flag, umode_t mode) +{ + struct dentry *const DENTRY_NOT_SET = (void *) -1UL; + struct inode *dir = nd->path.dentry->d_inode; + int error; + + if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */ + open_flag &= ~O_TRUNC; + + if (nd->flags & LOOKUP_DIRECTORY) + open_flag |= O_DIRECTORY; + + file->f_path.dentry = DENTRY_NOT_SET; + file->f_path.mnt = nd->path.mnt; + error = dir->i_op->atomic_open(dir, dentry, file, + open_to_namei_flags(open_flag), mode); + d_lookup_done(dentry); + if (!error) { + if (file->f_mode & FMODE_OPENED) { + /* + * We didn't have the inode before the open, so check open + * permission here. + */ + int acc_mode = op->acc_mode; + if (file->f_mode & FMODE_CREATED) { + WARN_ON(!(open_flag & O_CREAT)); + fsnotify_create(dir, dentry); + acc_mode = 0; + } + error = may_open(&file->f_path, acc_mode, open_flag); + if (WARN_ON(error > 0)) + error = -EINVAL; + } else if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { + error = -EIO; + } else { + if (file->f_path.dentry) { + dput(dentry); + dentry = file->f_path.dentry; + } + if (file->f_mode & FMODE_CREATED) + fsnotify_create(dir, dentry); + if (unlikely(d_is_negative(dentry))) { + error = -ENOENT; + } else { + path->dentry = dentry; + path->mnt = nd->path.mnt; + return 0; + } + } + } + dput(dentry); + return error; +} + +/* + * Look up and maybe create and open the last component. + * + * Must be called with parent locked (exclusive in O_CREAT case). + * + * Returns 0 on success, that is, if + * the file was successfully atomically created (if necessary) and opened, or + * the file was not completely opened at this time, though lookups and + * creations were performed. + * These case are distinguished by presence of FMODE_OPENED on file->f_mode. + * In the latter case dentry returned in @path might be negative if O_CREAT + * hadn't been specified. + * + * An error code is returned on failure. + */ +static int lookup_open(struct nameidata *nd, struct path *path, + struct file *file, + const struct open_flags *op, + bool got_write) +{ + struct dentry *dir = nd->path.dentry; + struct inode *dir_inode = dir->d_inode; + int open_flag = op->open_flag; + struct dentry *dentry; + int error, create_error = 0; + umode_t mode = op->mode; + DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); + + if (unlikely(IS_DEADDIR(dir_inode))) + return -ENOENT; + + file->f_mode &= ~FMODE_CREATED; + dentry = d_lookup(dir, &nd->last); + for (;;) { + if (!dentry) { + dentry = d_alloc_parallel(dir, &nd->last, &wq); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + } + if (d_in_lookup(dentry)) + break; + + error = d_revalidate(dentry, nd->flags); + if (likely(error > 0)) + break; + if (error) + goto out_dput; + d_invalidate(dentry); + dput(dentry); + dentry = NULL; + } + if (dentry->d_inode) { + /* Cached positive dentry: will open in f_op->open */ + goto out_no_open; + } + + /* + * Checking write permission is tricky, bacuse we don't know if we are + * going to actually need it: O_CREAT opens should work as long as the + * file exists. But checking existence breaks atomicity. The trick is + * to check access and if not granted clear O_CREAT from the flags. + * + * Another problem is returing the "right" error value (e.g. for an + * O_EXCL open we want to return EEXIST not EROFS). + */ + if (open_flag & O_CREAT) { + if (!IS_POSIXACL(dir->d_inode)) + mode &= ~current_umask(); + if (unlikely(!got_write)) { + create_error = -EROFS; + open_flag &= ~O_CREAT; + if (open_flag & (O_EXCL | O_TRUNC)) + goto no_open; + /* No side effects, safe to clear O_CREAT */ + } else { + create_error = may_o_create(&nd->path, dentry, mode); + if (create_error) { + open_flag &= ~O_CREAT; + if (open_flag & O_EXCL) + goto no_open; + } + } + } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) && + unlikely(!got_write)) { + /* + * No O_CREATE -> atomicity not a requirement -> fall + * back to lookup + open + */ + goto no_open; + } + + if (dir_inode->i_op->atomic_open) { + error = atomic_open(nd, dentry, path, file, op, open_flag, + mode); + if (unlikely(error == -ENOENT) && create_error) + error = create_error; + return error; + } + +no_open: + if (d_in_lookup(dentry)) { + struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry, + nd->flags); + d_lookup_done(dentry); + if (unlikely(res)) { + if (IS_ERR(res)) { + error = PTR_ERR(res); + goto out_dput; + } + dput(dentry); + dentry = res; + } + } + + /* Negative dentry, just create the file */ + if (!dentry->d_inode && (open_flag & O_CREAT)) { + file->f_mode |= FMODE_CREATED; + audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE); + if (!dir_inode->i_op->create) { + error = -EACCES; + goto out_dput; + } + error = dir_inode->i_op->create(dir_inode, dentry, mode, + open_flag & O_EXCL); + if (error) + goto out_dput; + fsnotify_create(dir_inode, dentry); + } + if (unlikely(create_error) && !dentry->d_inode) { + error = create_error; + goto out_dput; + } +out_no_open: + path->dentry = dentry; + path->mnt = nd->path.mnt; + return 0; + +out_dput: + dput(dentry); + return error; +} + +/* + * Handle the last step of open() + */ +static int do_last(struct nameidata *nd, + struct file *file, const struct open_flags *op) +{ + struct dentry *dir = nd->path.dentry; + kuid_t dir_uid = nd->inode->i_uid; + umode_t dir_mode = nd->inode->i_mode; + int open_flag = op->open_flag; + bool will_truncate = (open_flag & O_TRUNC) != 0; + bool got_write = false; + int acc_mode = op->acc_mode; + unsigned seq; + struct inode *inode; + struct path path; + int error; + + nd->flags &= ~LOOKUP_PARENT; + nd->flags |= op->intent; + + if (nd->last_type != LAST_NORM) { + error = handle_dots(nd, nd->last_type); + if (unlikely(error)) + return error; + goto finish_open; + } + + if (!(open_flag & O_CREAT)) { + if (nd->last.name[nd->last.len]) + nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; + /* we _can_ be in RCU mode here */ + error = lookup_fast(nd, &path, &inode, &seq); + if (likely(error > 0)) + goto finish_lookup; + + if (error < 0) + return error; + + BUG_ON(nd->inode != dir->d_inode); + BUG_ON(nd->flags & LOOKUP_RCU); + } else { + /* create side of things */ + /* + * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED + * has been cleared when we got to the last component we are + * about to look up + */ + error = complete_walk(nd); + if (error) + return error; + + audit_inode(nd->name, dir, LOOKUP_PARENT); + /* trailing slashes? */ + if (unlikely(nd->last.name[nd->last.len])) + return -EISDIR; + } + + if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { + error = mnt_want_write(nd->path.mnt); + if (!error) + got_write = true; + /* + * do _not_ fail yet - we might not need that or fail with + * a different error; let lookup_open() decide; we'll be + * dropping this one anyway. + */ + } + if (open_flag & O_CREAT) + inode_lock(dir->d_inode); + else + inode_lock_shared(dir->d_inode); + error = lookup_open(nd, &path, file, op, got_write); + if (open_flag & O_CREAT) + inode_unlock(dir->d_inode); + else + inode_unlock_shared(dir->d_inode); + + if (error) + goto out; + + if (file->f_mode & FMODE_OPENED) { + if ((file->f_mode & FMODE_CREATED) || + !S_ISREG(file_inode(file)->i_mode)) + will_truncate = false; + + audit_inode(nd->name, file->f_path.dentry, 0); + goto opened; + } + + if (file->f_mode & FMODE_CREATED) { + /* Don't check for write permission, don't truncate */ + open_flag &= ~O_TRUNC; + will_truncate = false; + acc_mode = 0; + path_to_nameidata(&path, nd); + goto finish_open_created; + } + + /* + * If atomic_open() acquired write access it is dropped now due to + * possible mount and symlink following (this might be optimized away if + * necessary...) + */ + if (got_write) { + mnt_drop_write(nd->path.mnt); + got_write = false; + } + + error = follow_managed(&path, nd); + if (unlikely(error < 0)) + return error; + + if (unlikely(d_is_negative(path.dentry))) { + path_to_nameidata(&path, nd); + return -ENOENT; + } + + /* + * create/update audit record if it already exists. + */ + audit_inode(nd->name, path.dentry, 0); + + if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) { + path_to_nameidata(&path, nd); + return -EEXIST; + } + + seq = 0; /* out of RCU mode, so the value doesn't matter */ + inode = d_backing_inode(path.dentry); +finish_lookup: + error = step_into(nd, &path, 0, inode, seq); + if (unlikely(error)) + return error; +finish_open: + /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ + error = complete_walk(nd); + if (error) + return error; + audit_inode(nd->name, nd->path.dentry, 0); + if (open_flag & O_CREAT) { + error = -EISDIR; + if (d_is_dir(nd->path.dentry)) + goto out; + error = may_create_in_sticky(dir_mode, dir_uid, + d_backing_inode(nd->path.dentry)); + if (unlikely(error)) + goto out; + } + error = -ENOTDIR; + if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) + goto out; + if (!d_is_reg(nd->path.dentry)) + will_truncate = false; + + if (will_truncate) { + error = mnt_want_write(nd->path.mnt); + if (error) + goto out; + got_write = true; + } +finish_open_created: + error = may_open(&nd->path, acc_mode, open_flag); + if (error) + goto out; + BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */ + error = vfs_open(&nd->path, file); + if (error) + goto out; +opened: + error = ima_file_check(file, op->acc_mode); + if (!error && will_truncate) + error = handle_truncate(file); +out: + if (unlikely(error > 0)) { + WARN_ON(1); + error = -EINVAL; + } + if (got_write) + mnt_drop_write(nd->path.mnt); + return error; +} + +struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode, int open_flag) +{ + struct dentry *child = NULL; + struct inode *dir = dentry->d_inode; + struct inode *inode; + int error; + + /* we want directory to be writable */ + error = inode_permission(dir, MAY_WRITE | MAY_EXEC); + if (error) + goto out_err; + error = -EOPNOTSUPP; + if (!dir->i_op->tmpfile) + goto out_err; + error = -ENOMEM; + child = d_alloc(dentry, &slash_name); + if (unlikely(!child)) + goto out_err; + error = dir->i_op->tmpfile(dir, child, mode); + if (error) + goto out_err; + error = -ENOENT; + inode = child->d_inode; + if (unlikely(!inode)) + goto out_err; + if (!(open_flag & O_EXCL)) { + spin_lock(&inode->i_lock); + inode->i_state |= I_LINKABLE; + spin_unlock(&inode->i_lock); + } + return child; + +out_err: + dput(child); + return ERR_PTR(error); +} +EXPORT_SYMBOL(vfs_tmpfile); + +static int do_tmpfile(struct nameidata *nd, unsigned flags, + const struct open_flags *op, + struct file *file) +{ + struct dentry *child; + struct path path; + int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path); + if (unlikely(error)) + return error; + error = mnt_want_write(path.mnt); + if (unlikely(error)) + goto out; + child = vfs_tmpfile(path.dentry, op->mode, op->open_flag); + error = PTR_ERR(child); + if (IS_ERR(child)) + goto out2; + dput(path.dentry); + path.dentry = child; + audit_inode(nd->name, child, 0); + /* Don't check for other permissions, the inode was just created */ + error = may_open(&path, 0, op->open_flag); + if (error) + goto out2; + file->f_path.mnt = path.mnt; + error = finish_open(file, child, NULL); +out2: + mnt_drop_write(path.mnt); +out: + path_put(&path); + return error; +} + +static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file) +{ + struct path path; + int error = path_lookupat(nd, flags, &path); + if (!error) { + audit_inode(nd->name, path.dentry, 0); + error = vfs_open(&path, file); + path_put(&path); + } + return error; +} + +static struct file *path_openat(struct nameidata *nd, + const struct open_flags *op, unsigned flags) +{ + struct file *file; + int error; + + file = alloc_empty_file(op->open_flag, current_cred()); + if (IS_ERR(file)) + return file; + + if (unlikely(file->f_flags & __O_TMPFILE)) { + error = do_tmpfile(nd, flags, op, file); + } else if (unlikely(file->f_flags & O_PATH)) { + error = do_o_path(nd, flags, file); + } else { + const char *s = path_init(nd, flags); + while (!(error = link_path_walk(s, nd)) && + (error = do_last(nd, file, op)) > 0) { + nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); + s = trailing_symlink(nd); + } + terminate_walk(nd); + } + if (likely(!error)) { + if (likely(file->f_mode & FMODE_OPENED)) + return file; + WARN_ON(1); + error = -EINVAL; + } + fput(file); + if (error == -EOPENSTALE) { + if (flags & LOOKUP_RCU) + error = -ECHILD; + else + error = -ESTALE; + } + return ERR_PTR(error); +} + +struct file *do_filp_open(int dfd, struct filename *pathname, + const struct open_flags *op) +{ + struct nameidata nd; + int flags = op->lookup_flags; + struct file *filp; + + set_nameidata(&nd, dfd, pathname); + filp = path_openat(&nd, op, flags | LOOKUP_RCU); + if (unlikely(filp == ERR_PTR(-ECHILD))) + filp = path_openat(&nd, op, flags); + if (unlikely(filp == ERR_PTR(-ESTALE))) + filp = path_openat(&nd, op, flags | LOOKUP_REVAL); + restore_nameidata(); + return filp; +} + +struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, + const char *name, const struct open_flags *op) +{ + struct nameidata nd; + struct file *file; + struct filename *filename; + int flags = op->lookup_flags | LOOKUP_ROOT; + + nd.root.mnt = mnt; + nd.root.dentry = dentry; + + if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN) + return ERR_PTR(-ELOOP); + + filename = getname_kernel(name); + if (IS_ERR(filename)) + return ERR_CAST(filename); + + set_nameidata(&nd, -1, filename); + file = path_openat(&nd, op, flags | LOOKUP_RCU); + if (unlikely(file == ERR_PTR(-ECHILD))) + file = path_openat(&nd, op, flags); + if (unlikely(file == ERR_PTR(-ESTALE))) + file = path_openat(&nd, op, flags | LOOKUP_REVAL); + restore_nameidata(); + putname(filename); + return file; +} + +static struct dentry *filename_create(int dfd, struct filename *name, + struct path *path, unsigned int lookup_flags) +{ + struct dentry *dentry = ERR_PTR(-EEXIST); + struct qstr last; + int type; + int err2; + int error; + bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); + + /* + * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any + * other flags passed in are ignored! + */ + lookup_flags &= LOOKUP_REVAL; + + name = filename_parentat(dfd, name, lookup_flags, path, &last, &type); + if (IS_ERR(name)) + return ERR_CAST(name); + + /* + * Yucky last component or no last component at all? + * (foo/., foo/.., /////) + */ + if (unlikely(type != LAST_NORM)) + goto out; + + /* don't fail immediately if it's r/o, at least try to report other errors */ + err2 = mnt_want_write(path->mnt); + /* + * Do the final lookup. + */ + lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL; + inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); + dentry = __lookup_hash(&last, path->dentry, lookup_flags); + if (IS_ERR(dentry)) + goto unlock; + + error = -EEXIST; + if (d_is_positive(dentry)) + goto fail; + + /* + * Special case - lookup gave negative, but... we had foo/bar/ + * From the vfs_mknod() POV we just have a negative dentry - + * all is fine. Let's be bastards - you had / on the end, you've + * been asking for (non-existent) directory. -ENOENT for you. + */ + if (unlikely(!is_dir && last.name[last.len])) { + error = -ENOENT; + goto fail; + } + if (unlikely(err2)) { + error = err2; + goto fail; + } + putname(name); + return dentry; +fail: + dput(dentry); + dentry = ERR_PTR(error); +unlock: + inode_unlock(path->dentry->d_inode); + if (!err2) + mnt_drop_write(path->mnt); +out: + path_put(path); + putname(name); + return dentry; +} + +struct dentry *kern_path_create(int dfd, const char *pathname, + struct path *path, unsigned int lookup_flags) +{ + return filename_create(dfd, getname_kernel(pathname), + path, lookup_flags); +} +EXPORT_SYMBOL(kern_path_create); + +void done_path_create(struct path *path, struct dentry *dentry) +{ + dput(dentry); + inode_unlock(path->dentry->d_inode); + mnt_drop_write(path->mnt); + path_put(path); +} +EXPORT_SYMBOL(done_path_create); + +inline struct dentry *user_path_create(int dfd, const char __user *pathname, + struct path *path, unsigned int lookup_flags) +{ + return filename_create(dfd, getname(pathname), path, lookup_flags); +} +EXPORT_SYMBOL(user_path_create); + +int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) +{ + int error = may_create(dir, dentry); + + if (error) + return error; + + if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) + return -EPERM; + + if (!dir->i_op->mknod) + return -EPERM; + + error = devcgroup_inode_mknod(mode, dev); + if (error) + return error; + + error = security_inode_mknod(dir, dentry, mode, dev); + if (error) + return error; + + error = dir->i_op->mknod(dir, dentry, mode, dev); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_mknod); + +static int may_mknod(umode_t mode) +{ + switch (mode & S_IFMT) { + case S_IFREG: + case S_IFCHR: + case S_IFBLK: + case S_IFIFO: + case S_IFSOCK: + case 0: /* zero mode translates to S_IFREG */ + return 0; + case S_IFDIR: + return -EPERM; + default: + return -EINVAL; + } +} + +long do_mknodat(int dfd, const char __user *filename, umode_t mode, + unsigned int dev) +{ + struct dentry *dentry; + struct path path; + int error; + unsigned int lookup_flags = 0; + + error = may_mknod(mode); + if (error) + return error; +retry: + dentry = user_path_create(dfd, filename, &path, lookup_flags); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + + if (!IS_POSIXACL(path.dentry->d_inode)) + mode &= ~current_umask(); + error = security_path_mknod(&path, dentry, mode, dev); + if (error) + goto out; + switch (mode & S_IFMT) { + case 0: case S_IFREG: + error = vfs_create(path.dentry->d_inode,dentry,mode,true); + if (!error) + ima_post_path_mknod(dentry); + break; + case S_IFCHR: case S_IFBLK: + error = vfs_mknod(path.dentry->d_inode,dentry,mode, + new_decode_dev(dev)); + break; + case S_IFIFO: case S_IFSOCK: + error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); + break; + } +out: + done_path_create(&path, dentry); + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, + unsigned int, dev) +{ + return do_mknodat(dfd, filename, mode, dev); +} + +SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) +{ + return do_mknodat(AT_FDCWD, filename, mode, dev); +} + +int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) +{ + int error = may_create(dir, dentry); + unsigned max_links = dir->i_sb->s_max_links; + + if (error) + return error; + + if (!dir->i_op->mkdir) + return -EPERM; + + mode &= (S_IRWXUGO|S_ISVTX); + error = security_inode_mkdir(dir, dentry, mode); + if (error) + return error; + + if (max_links && dir->i_nlink >= max_links) + return -EMLINK; + + error = dir->i_op->mkdir(dir, dentry, mode); + if (!error) + fsnotify_mkdir(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_mkdir); + +long do_mkdirat(int dfd, const char __user *pathname, umode_t mode) +{ + struct dentry *dentry; + struct path path; + int error; + unsigned int lookup_flags = LOOKUP_DIRECTORY; + +retry: + dentry = user_path_create(dfd, pathname, &path, lookup_flags); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + + if (!IS_POSIXACL(path.dentry->d_inode)) + mode &= ~current_umask(); + error = security_path_mkdir(&path, dentry, mode); + if (!error) + error = vfs_mkdir(path.dentry->d_inode, dentry, mode); + done_path_create(&path, dentry); + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) +{ + return do_mkdirat(dfd, pathname, mode); +} + +SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) +{ + return do_mkdirat(AT_FDCWD, pathname, mode); +} + +int vfs_rmdir(struct inode *dir, struct dentry *dentry) +{ + int error = may_delete(dir, dentry, 1); + + if (error) + return error; + + if (!dir->i_op->rmdir) + return -EPERM; + + dget(dentry); + inode_lock(dentry->d_inode); + + error = -EBUSY; + if (is_local_mountpoint(dentry)) + goto out; + + error = security_inode_rmdir(dir, dentry); + if (error) + goto out; + + error = dir->i_op->rmdir(dir, dentry); + if (error) + goto out; + + shrink_dcache_parent(dentry); + dentry->d_inode->i_flags |= S_DEAD; + dont_mount(dentry); + detach_mounts(dentry); + +out: + inode_unlock(dentry->d_inode); + dput(dentry); + if (!error) + d_delete(dentry); + return error; +} +EXPORT_SYMBOL(vfs_rmdir); + +long do_rmdir(int dfd, const char __user *pathname) +{ + int error = 0; + struct filename *name; + struct dentry *dentry; + struct path path; + struct qstr last; + int type; + unsigned int lookup_flags = 0; +retry: + name = filename_parentat(dfd, getname(pathname), lookup_flags, + &path, &last, &type); + if (IS_ERR(name)) + return PTR_ERR(name); + + switch (type) { + case LAST_DOTDOT: + error = -ENOTEMPTY; + goto exit1; + case LAST_DOT: + error = -EINVAL; + goto exit1; + case LAST_ROOT: + error = -EBUSY; + goto exit1; + } + + error = mnt_want_write(path.mnt); + if (error) + goto exit1; + + inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); + dentry = __lookup_hash(&last, path.dentry, lookup_flags); + error = PTR_ERR(dentry); + if (IS_ERR(dentry)) + goto exit2; + if (!dentry->d_inode) { + error = -ENOENT; + goto exit3; + } + error = security_path_rmdir(&path, dentry); + if (error) + goto exit3; + error = vfs_rmdir(path.dentry->d_inode, dentry); +exit3: + dput(dentry); +exit2: + inode_unlock(path.dentry->d_inode); + mnt_drop_write(path.mnt); +exit1: + path_put(&path); + putname(name); + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } + return error; +} + +SYSCALL_DEFINE1(rmdir, const char __user *, pathname) +{ + return do_rmdir(AT_FDCWD, pathname); +} + +/** + * vfs_unlink - unlink a filesystem object + * @dir: parent directory + * @dentry: victim + * @delegated_inode: returns victim inode, if the inode is delegated. + * + * The caller must hold dir->i_mutex. + * + * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and + * return a reference to the inode in delegated_inode. The caller + * should then break the delegation on that inode and retry. Because + * breaking a delegation may take a long time, the caller should drop + * dir->i_mutex before doing so. + * + * Alternatively, a caller may pass NULL for delegated_inode. This may + * be appropriate for callers that expect the underlying filesystem not + * to be NFS exported. + */ +int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode) +{ + struct inode *target = dentry->d_inode; + int error = may_delete(dir, dentry, 0); + + if (error) + return error; + + if (!dir->i_op->unlink) + return -EPERM; + + inode_lock(target); + if (is_local_mountpoint(dentry)) + error = -EBUSY; + else { + error = security_inode_unlink(dir, dentry); + if (!error) { + error = try_break_deleg(target, delegated_inode); + if (error) + goto out; + error = dir->i_op->unlink(dir, dentry); + if (!error) { + dont_mount(dentry); + detach_mounts(dentry); + } + } + } +out: + inode_unlock(target); + + /* We don't d_delete() NFS sillyrenamed files--they still exist. */ + if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { + fsnotify_link_count(target); + d_delete(dentry); + } + + return error; +} +EXPORT_SYMBOL(vfs_unlink); + +/* + * Make sure that the actual truncation of the file will occur outside its + * directory's i_mutex. Truncate can take a long time if there is a lot of + * writeout happening, and we don't want to prevent access to the directory + * while waiting on the I/O. + */ +long do_unlinkat(int dfd, struct filename *name) +{ + int error; + struct dentry *dentry; + struct path path; + struct qstr last; + int type; + struct inode *inode = NULL; + struct inode *delegated_inode = NULL; + unsigned int lookup_flags = 0; +retry: + name = filename_parentat(dfd, name, lookup_flags, &path, &last, &type); + if (IS_ERR(name)) + return PTR_ERR(name); + + error = -EISDIR; + if (type != LAST_NORM) + goto exit1; + + error = mnt_want_write(path.mnt); + if (error) + goto exit1; +retry_deleg: + inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); + dentry = __lookup_hash(&last, path.dentry, lookup_flags); + error = PTR_ERR(dentry); + if (!IS_ERR(dentry)) { + /* Why not before? Because we want correct error value */ + if (last.name[last.len]) + goto slashes; + inode = dentry->d_inode; + if (d_is_negative(dentry)) + goto slashes; + ihold(inode); + error = security_path_unlink(&path, dentry); + if (error) + goto exit2; + error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode); +exit2: + dput(dentry); + } + inode_unlock(path.dentry->d_inode); + if (inode) + iput(inode); /* truncate the inode here */ + inode = NULL; + if (delegated_inode) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry_deleg; + } + mnt_drop_write(path.mnt); +exit1: + path_put(&path); + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + inode = NULL; + goto retry; + } + putname(name); + return error; + +slashes: + if (d_is_negative(dentry)) + error = -ENOENT; + else if (d_is_dir(dentry)) + error = -EISDIR; + else + error = -ENOTDIR; + goto exit2; +} + +SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) +{ + if ((flag & ~AT_REMOVEDIR) != 0) + return -EINVAL; + + if (flag & AT_REMOVEDIR) + return do_rmdir(dfd, pathname); + + return do_unlinkat(dfd, getname(pathname)); +} + +SYSCALL_DEFINE1(unlink, const char __user *, pathname) +{ + return do_unlinkat(AT_FDCWD, getname(pathname)); +} + +int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) +{ + int error = may_create(dir, dentry); + + if (error) + return error; + + if (!dir->i_op->symlink) + return -EPERM; + + error = security_inode_symlink(dir, dentry, oldname); + if (error) + return error; + + error = dir->i_op->symlink(dir, dentry, oldname); + if (!error) + fsnotify_create(dir, dentry); + return error; +} +EXPORT_SYMBOL(vfs_symlink); + +long do_symlinkat(const char __user *oldname, int newdfd, + const char __user *newname) +{ + int error; + struct filename *from; + struct dentry *dentry; + struct path path; + unsigned int lookup_flags = 0; + + from = getname(oldname); + if (IS_ERR(from)) + return PTR_ERR(from); +retry: + dentry = user_path_create(newdfd, newname, &path, lookup_flags); + error = PTR_ERR(dentry); + if (IS_ERR(dentry)) + goto out_putname; + + error = security_path_symlink(&path, dentry, from->name); + if (!error) + error = vfs_symlink(path.dentry->d_inode, dentry, from->name); + done_path_create(&path, dentry); + if (retry_estale(error, lookup_flags)) { + lookup_flags |= LOOKUP_REVAL; + goto retry; + } +out_putname: + putname(from); + return error; +} + +SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, + int, newdfd, const char __user *, newname) +{ + return do_symlinkat(oldname, newdfd, newname); +} + +SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) +{ + return do_symlinkat(oldname, AT_FDCWD, newname); +} + +/** + * vfs_link - create a new link + * @old_dentry: object to be linked + * @dir: new parent + * @new_dentry: where to create the new link + * @delegated_inode: returns inode needing a delegation break + * + * The caller must hold dir->i_mutex + * + * If vfs_link discovers a delegation on the to-be-linked file in need + * of breaking, it will return -EWOULDBLOCK and return a reference to the + * inode in delegated_inode. The caller should then break the delegation + * and retry. Because breaking a delegation may take a long time, the + * caller should drop the i_mutex before doing so. + * + * Alternatively, a caller may pass NULL for delegated_inode. This may + * be appropriate for callers that expect the underlying filesystem not + * to be NFS exported. + */ +int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode) +{ + struct inode *inode = old_dentry->d_inode; + unsigned max_links = dir->i_sb->s_max_links; + int error; + + if (!inode) + return -ENOENT; + + error = may_create(dir, new_dentry); + if (error) + return error; + + if (dir->i_sb != inode->i_sb) + return -EXDEV; + + /* + * A link to an append-only or immutable file cannot be created. + */ + if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) + return -EPERM; + /* + * Updating the link count will likely cause i_uid and i_gid to + * be writen back improperly if their true value is unknown to + * the vfs. + */ + if (HAS_UNMAPPED_ID(inode)) + return -EPERM; + if (!dir->i_op->link) + return -EPERM; + if (S_ISDIR(inode->i_mode)) + return -EPERM; + + error = security_inode_link(old_dentry, dir, new_dentry); + if (error) + return error; + + inode_lock(inode); + /* Make sure we don't allow creating hardlink to an unlinked file */ + if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE)) + error = -ENOENT; + else if (max_links && inode->i_nlink >= max_links) + error = -EMLINK; + else { + error = try_break_deleg(inode, delegated_inode); + if (!error) + error = dir->i_op->link(old_dentry, dir, new_dentry); + } + + if (!error && (inode->i_state & I_LINKABLE)) { + spin_lock(&inode->i_lock); + inode->i_state &= ~I_LINKABLE; + spin_unlock(&inode->i_lock); + } + inode_unlock(inode); + if (!error) + fsnotify_link(dir, inode, new_dentry); + return error; +} +EXPORT_SYMBOL(vfs_link); + +/* + * Hardlinks are often used in delicate situations. We avoid + * security-related surprises by not following symlinks on the + * newname. --KAB + * + * We don't follow them on the oldname either to be compatible + * with linux 2.0, and to avoid hard-linking to directories + * and other special files. --ADM + */ +int do_linkat(int olddfd, const char __user *oldname, int newdfd, + const char __user *newname, int flags) +{ + struct dentry *new_dentry; + struct path old_path, new_path; + struct inode *delegated_inode = NULL; + int how = 0; + int error; + + if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) + return -EINVAL; + /* + * To use null names we require CAP_DAC_READ_SEARCH + * This ensures that not everyone will be able to create + * handlink using the passed filedescriptor. + */ + if (flags & AT_EMPTY_PATH) { + if (!capable(CAP_DAC_READ_SEARCH)) + return -ENOENT; + how = LOOKUP_EMPTY; + } + + if (flags & AT_SYMLINK_FOLLOW) + how |= LOOKUP_FOLLOW; +retry: + error = user_path_at(olddfd, oldname, how, &old_path); + if (error) + return error; + + new_dentry = user_path_create(newdfd, newname, &new_path, + (how & LOOKUP_REVAL)); + error = PTR_ERR(new_dentry); + if (IS_ERR(new_dentry)) + goto out; + + error = -EXDEV; + if (old_path.mnt != new_path.mnt) + goto out_dput; + error = may_linkat(&old_path); + if (unlikely(error)) + goto out_dput; + error = security_path_link(old_path.dentry, &new_path, new_dentry); + if (error) + goto out_dput; + error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode); +out_dput: + done_path_create(&new_path, new_dentry); + if (delegated_inode) { + error = break_deleg_wait(&delegated_inode); + if (!error) { + path_put(&old_path); + goto retry; + } + } + if (retry_estale(error, how)) { + path_put(&old_path); + how |= LOOKUP_REVAL; + goto retry; + } +out: + path_put(&old_path); + + return error; +} + +SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, + int, newdfd, const char __user *, newname, int, flags) +{ + return do_linkat(olddfd, oldname, newdfd, newname, flags); +} + +SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) +{ + return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); +} + +/** + * vfs_rename - rename a filesystem object + * @old_dir: parent of source + * @old_dentry: source + * @new_dir: parent of destination + * @new_dentry: destination + * @delegated_inode: returns an inode needing a delegation break + * @flags: rename flags + * + * The caller must hold multiple mutexes--see lock_rename()). + * + * If vfs_rename discovers a delegation in need of breaking at either + * the source or destination, it will return -EWOULDBLOCK and return a + * reference to the inode in delegated_inode. The caller should then + * break the delegation and retry. Because breaking a delegation may + * take a long time, the caller should drop all locks before doing + * so. + * + * Alternatively, a caller may pass NULL for delegated_inode. This may + * be appropriate for callers that expect the underlying filesystem not + * to be NFS exported. + * + * The worst of all namespace operations - renaming directory. "Perverted" + * doesn't even start to describe it. Somebody in UCB had a heck of a trip... + * Problems: + * + * a) we can get into loop creation. + * b) race potential - two innocent renames can create a loop together. + * That's where 4.4 screws up. Current fix: serialization on + * sb->s_vfs_rename_mutex. We might be more accurate, but that's another + * story. + * c) we have to lock _four_ objects - parents and victim (if it exists), + * and source (if it is not a directory). + * And that - after we got ->i_mutex on parents (until then we don't know + * whether the target exists). Solution: try to be smart with locking + * order for inodes. We rely on the fact that tree topology may change + * only under ->s_vfs_rename_mutex _and_ that parent of the object we + * move will be locked. Thus we can rank directories by the tree + * (ancestors first) and rank all non-directories after them. + * That works since everybody except rename does "lock parent, lookup, + * lock child" and rename is under ->s_vfs_rename_mutex. + * HOWEVER, it relies on the assumption that any object with ->lookup() + * has no more than 1 dentry. If "hybrid" objects will ever appear, + * we'd better make sure that there's no link(2) for them. + * d) conversion from fhandle to dentry may come in the wrong moment - when + * we are removing the target. Solution: we will have to grab ->i_mutex + * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on + * ->i_mutex on parents, which works but leads to some truly excessive + * locking]. + */ +int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry, + struct inode **delegated_inode, unsigned int flags) +{ + int error; + bool is_dir = d_is_dir(old_dentry); + struct inode *source = old_dentry->d_inode; + struct inode *target = new_dentry->d_inode; + bool new_is_dir = false; + unsigned max_links = new_dir->i_sb->s_max_links; + struct name_snapshot old_name; + + if (source == target) + return 0; + + error = may_delete(old_dir, old_dentry, is_dir); + if (error) + return error; + + if (!target) { + error = may_create(new_dir, new_dentry); + } else { + new_is_dir = d_is_dir(new_dentry); + + if (!(flags & RENAME_EXCHANGE)) + error = may_delete(new_dir, new_dentry, is_dir); + else + error = may_delete(new_dir, new_dentry, new_is_dir); + } + if (error) + return error; + + if (!old_dir->i_op->rename) + return -EPERM; + + /* + * If we are going to change the parent - check write permissions, + * we'll need to flip '..'. + */ + if (new_dir != old_dir) { + if (is_dir) { + error = inode_permission(source, MAY_WRITE); + if (error) + return error; + } + if ((flags & RENAME_EXCHANGE) && new_is_dir) { + error = inode_permission(target, MAY_WRITE); + if (error) + return error; + } + } + + error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry, + flags); + if (error) + return error; + + take_dentry_name_snapshot(&old_name, old_dentry); + dget(new_dentry); + if (!is_dir || (flags & RENAME_EXCHANGE)) + lock_two_nondirectories(source, target); + else if (target) + inode_lock(target); + + error = -EBUSY; + if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry)) + goto out; + + if (max_links && new_dir != old_dir) { + error = -EMLINK; + if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links) + goto out; + if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir && + old_dir->i_nlink >= max_links) + goto out; + } + if (!is_dir) { + error = try_break_deleg(source, delegated_inode); + if (error) + goto out; + } + if (target && !new_is_dir) { + error = try_break_deleg(target, delegated_inode); + if (error) + goto out; + } + error = old_dir->i_op->rename(old_dir, old_dentry, + new_dir, new_dentry, flags); + if (error) + goto out; + + if (!(flags & RENAME_EXCHANGE) && target) { + if (is_dir) { + shrink_dcache_parent(new_dentry); + target->i_flags |= S_DEAD; + } + dont_mount(new_dentry); + detach_mounts(new_dentry); + } + if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) { + if (!(flags & RENAME_EXCHANGE)) + d_move(old_dentry, new_dentry); + else + d_exchange(old_dentry, new_dentry); + } +out: + if (!is_dir || (flags & RENAME_EXCHANGE)) + unlock_two_nondirectories(source, target); + else if (target) + inode_unlock(target); + dput(new_dentry); + if (!error) { + fsnotify_move(old_dir, new_dir, old_name.name, is_dir, + !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); + if (flags & RENAME_EXCHANGE) { + fsnotify_move(new_dir, old_dir, old_dentry->d_name.name, + new_is_dir, NULL, new_dentry); + } + } + release_dentry_name_snapshot(&old_name); + + return error; +} +EXPORT_SYMBOL(vfs_rename); + +static int do_renameat2(int olddfd, const char __user *oldname, int newdfd, + const char __user *newname, unsigned int flags) +{ + struct dentry *old_dentry, *new_dentry; + struct dentry *trap; + struct path old_path, new_path; + struct qstr old_last, new_last; + int old_type, new_type; + struct inode *delegated_inode = NULL; + struct filename *from; + struct filename *to; + unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET; + bool should_retry = false; + int error; + + if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) + return -EINVAL; + + if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) && + (flags & RENAME_EXCHANGE)) + return -EINVAL; + + if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD)) + return -EPERM; + + if (flags & RENAME_EXCHANGE) + target_flags = 0; + +retry: + from = filename_parentat(olddfd, getname(oldname), lookup_flags, + &old_path, &old_last, &old_type); + if (IS_ERR(from)) { + error = PTR_ERR(from); + goto exit; + } + + to = filename_parentat(newdfd, getname(newname), lookup_flags, + &new_path, &new_last, &new_type); + if (IS_ERR(to)) { + error = PTR_ERR(to); + goto exit1; + } + + error = -EXDEV; + if (old_path.mnt != new_path.mnt) + goto exit2; + + error = -EBUSY; + if (old_type != LAST_NORM) + goto exit2; + + if (flags & RENAME_NOREPLACE) + error = -EEXIST; + if (new_type != LAST_NORM) + goto exit2; + + error = mnt_want_write(old_path.mnt); + if (error) + goto exit2; + +retry_deleg: + trap = lock_rename(new_path.dentry, old_path.dentry); + + old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags); + error = PTR_ERR(old_dentry); + if (IS_ERR(old_dentry)) + goto exit3; + /* source must exist */ + error = -ENOENT; + if (d_is_negative(old_dentry)) + goto exit4; + new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags); + error = PTR_ERR(new_dentry); + if (IS_ERR(new_dentry)) + goto exit4; + error = -EEXIST; + if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) + goto exit5; + if (flags & RENAME_EXCHANGE) { + error = -ENOENT; + if (d_is_negative(new_dentry)) + goto exit5; + + if (!d_is_dir(new_dentry)) { + error = -ENOTDIR; + if (new_last.name[new_last.len]) + goto exit5; + } + } + /* unless the source is a directory trailing slashes give -ENOTDIR */ + if (!d_is_dir(old_dentry)) { + error = -ENOTDIR; + if (old_last.name[old_last.len]) + goto exit5; + if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len]) + goto exit5; + } + /* source should not be ancestor of target */ + error = -EINVAL; + if (old_dentry == trap) + goto exit5; + /* target should not be an ancestor of source */ + if (!(flags & RENAME_EXCHANGE)) + error = -ENOTEMPTY; + if (new_dentry == trap) + goto exit5; + + error = security_path_rename(&old_path, old_dentry, + &new_path, new_dentry, flags); + if (error) + goto exit5; + error = vfs_rename(old_path.dentry->d_inode, old_dentry, + new_path.dentry->d_inode, new_dentry, + &delegated_inode, flags); +exit5: + dput(new_dentry); +exit4: + dput(old_dentry); +exit3: + unlock_rename(new_path.dentry, old_path.dentry); + if (delegated_inode) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry_deleg; + } + mnt_drop_write(old_path.mnt); +exit2: + if (retry_estale(error, lookup_flags)) + should_retry = true; + path_put(&new_path); + putname(to); +exit1: + path_put(&old_path); + putname(from); + if (should_retry) { + should_retry = false; + lookup_flags |= LOOKUP_REVAL; + goto retry; + } +exit: + return error; +} + +SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname, + int, newdfd, const char __user *, newname, unsigned int, flags) +{ + return do_renameat2(olddfd, oldname, newdfd, newname, flags); +} + +SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, + int, newdfd, const char __user *, newname) +{ + return do_renameat2(olddfd, oldname, newdfd, newname, 0); +} + +SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) +{ + return do_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0); +} + +int vfs_whiteout(struct inode *dir, struct dentry *dentry) +{ + int error = may_create(dir, dentry); + if (error) + return error; + + if (!dir->i_op->mknod) + return -EPERM; + + return dir->i_op->mknod(dir, dentry, + S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV); +} +EXPORT_SYMBOL(vfs_whiteout); + +int readlink_copy(char __user *buffer, int buflen, const char *link) +{ + int len = PTR_ERR(link); + if (IS_ERR(link)) + goto out; + + len = strlen(link); + if (len > (unsigned) buflen) + len = buflen; + if (copy_to_user(buffer, link, len)) + len = -EFAULT; +out: + return len; +} + +/** + * vfs_readlink - copy symlink body into userspace buffer + * @dentry: dentry on which to get symbolic link + * @buffer: user memory pointer + * @buflen: size of buffer + * + * Does not touch atime. That's up to the caller if necessary + * + * Does not call security hook. + */ +int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen) +{ + struct inode *inode = d_inode(dentry); + DEFINE_DELAYED_CALL(done); + const char *link; + int res; + + if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) { + if (unlikely(inode->i_op->readlink)) + return inode->i_op->readlink(dentry, buffer, buflen); + + if (!d_is_symlink(dentry)) + return -EINVAL; + + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_DEFAULT_READLINK; + spin_unlock(&inode->i_lock); + } + + link = inode->i_link; + if (!link) { + link = inode->i_op->get_link(dentry, inode, &done); + if (IS_ERR(link)) + return PTR_ERR(link); + } + res = readlink_copy(buffer, buflen, link); + do_delayed_call(&done); + return res; +} +EXPORT_SYMBOL(vfs_readlink); + +/** + * vfs_get_link - get symlink body + * @dentry: dentry on which to get symbolic link + * @done: caller needs to free returned data with this + * + * Calls security hook and i_op->get_link() on the supplied inode. + * + * It does not touch atime. That's up to the caller if necessary. + * + * Does not work on "special" symlinks like /proc/$$/fd/N + */ +const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done) +{ + const char *res = ERR_PTR(-EINVAL); + struct inode *inode = d_inode(dentry); + + if (d_is_symlink(dentry)) { + res = ERR_PTR(security_inode_readlink(dentry)); + if (!res) + res = inode->i_op->get_link(dentry, inode, done); + } + return res; +} +EXPORT_SYMBOL(vfs_get_link); + +/* get the link contents into pagecache */ +const char *page_get_link(struct dentry *dentry, struct inode *inode, + struct delayed_call *callback) +{ + char *kaddr; + struct page *page; + struct address_space *mapping = inode->i_mapping; + + if (!dentry) { + page = find_get_page(mapping, 0); + if (!page) + return ERR_PTR(-ECHILD); + if (!PageUptodate(page)) { + put_page(page); + return ERR_PTR(-ECHILD); + } + } else { + page = read_mapping_page(mapping, 0, NULL); + if (IS_ERR(page)) + return (char*)page; + } + set_delayed_call(callback, page_put_link, page); + BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM); + kaddr = page_address(page); + nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1); + return kaddr; +} + +EXPORT_SYMBOL(page_get_link); + +void page_put_link(void *arg) +{ + put_page(arg); +} +EXPORT_SYMBOL(page_put_link); + +int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) +{ + DEFINE_DELAYED_CALL(done); + int res = readlink_copy(buffer, buflen, + page_get_link(dentry, d_inode(dentry), + &done)); + do_delayed_call(&done); + return res; +} +EXPORT_SYMBOL(page_readlink); + +/* + * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS + */ +int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) +{ + struct address_space *mapping = inode->i_mapping; + struct page *page; + void *fsdata; + int err; + unsigned int flags = 0; + if (nofs) + flags |= AOP_FLAG_NOFS; + +retry: + err = pagecache_write_begin(NULL, mapping, 0, len-1, + flags, &page, &fsdata); + if (err) + goto fail; + + memcpy(page_address(page), symname, len-1); + + err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, + page, fsdata); + if (err < 0) + goto fail; + if (err < len-1) + goto retry; + + mark_inode_dirty(inode); + return 0; +fail: + return err; +} +EXPORT_SYMBOL(__page_symlink); + +int page_symlink(struct inode *inode, const char *symname, int len) +{ + return __page_symlink(inode, symname, len, + !mapping_gfp_constraint(inode->i_mapping, __GFP_FS)); +} +EXPORT_SYMBOL(page_symlink); + +const struct inode_operations page_symlink_inode_operations = { + .get_link = page_get_link, +}; +EXPORT_SYMBOL(page_symlink_inode_operations); |