diff options
Diffstat (limited to 'fs/overlayfs/super.c')
| -rw-r--r-- | fs/overlayfs/super.c | 1567 |
1 files changed, 1567 insertions, 0 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c new file mode 100644 index 0000000000..c71d185980 --- /dev/null +++ b/fs/overlayfs/super.c @@ -0,0 +1,1567 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * + * Copyright (C) 2011 Novell Inc. + */ + +#include <uapi/linux/magic.h> +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/xattr.h> +#include <linux/mount.h> +#include <linux/parser.h> +#include <linux/module.h> +#include <linux/statfs.h> +#include <linux/seq_file.h> +#include <linux/posix_acl_xattr.h> +#include <linux/exportfs.h> +#include <linux/file.h> +#include <linux/fs_context.h> +#include <linux/fs_parser.h> +#include "overlayfs.h" +#include "params.h" + +MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); +MODULE_DESCRIPTION("Overlay filesystem"); +MODULE_LICENSE("GPL"); + + +struct ovl_dir_cache; + +static struct dentry *ovl_d_real(struct dentry *dentry, + const struct inode *inode) +{ + struct dentry *real = NULL, *lower; + int err; + + /* It's an overlay file */ + if (inode && d_inode(dentry) == inode) + return dentry; + + if (!d_is_reg(dentry)) { + if (!inode || inode == d_inode(dentry)) + return dentry; + goto bug; + } + + real = ovl_dentry_upper(dentry); + if (real && (inode == d_inode(real))) + return real; + + if (real && !inode && ovl_has_upperdata(d_inode(dentry))) + return real; + + /* + * Best effort lazy lookup of lowerdata for !inode case to return + * the real lowerdata dentry. The only current caller of d_real() with + * NULL inode is d_real_inode() from trace_uprobe and this caller is + * likely going to be followed reading from the file, before placing + * uprobes on offset within the file, so lowerdata should be available + * when setting the uprobe. + */ + err = ovl_verify_lowerdata(dentry); + if (err) + goto bug; + lower = ovl_dentry_lowerdata(dentry); + if (!lower) + goto bug; + real = lower; + + /* Handle recursion */ + real = d_real(real, inode); + + if (!inode || inode == d_inode(real)) + return real; +bug: + WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n", + __func__, dentry, inode ? inode->i_sb->s_id : "NULL", + inode ? inode->i_ino : 0, real, + real && d_inode(real) ? d_inode(real)->i_ino : 0); + return dentry; +} + +static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak) +{ + int ret = 1; + + if (!d) + return 1; + + if (weak) { + if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) + ret = d->d_op->d_weak_revalidate(d, flags); + } else if (d->d_flags & DCACHE_OP_REVALIDATE) { + ret = d->d_op->d_revalidate(d, flags); + if (!ret) { + if (!(flags & LOOKUP_RCU)) + d_invalidate(d); + ret = -ESTALE; + } + } + return ret; +} + +static int ovl_dentry_revalidate_common(struct dentry *dentry, + unsigned int flags, bool weak) +{ + struct ovl_entry *oe; + struct ovl_path *lowerstack; + struct inode *inode = d_inode_rcu(dentry); + struct dentry *upper; + unsigned int i; + int ret = 1; + + /* Careful in RCU mode */ + if (!inode) + return -ECHILD; + + oe = OVL_I_E(inode); + lowerstack = ovl_lowerstack(oe); + upper = ovl_i_dentry_upper(inode); + if (upper) + ret = ovl_revalidate_real(upper, flags, weak); + + for (i = 0; ret > 0 && i < ovl_numlower(oe); i++) + ret = ovl_revalidate_real(lowerstack[i].dentry, flags, weak); + + return ret; +} + +static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags) +{ + return ovl_dentry_revalidate_common(dentry, flags, false); +} + +static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags) +{ + return ovl_dentry_revalidate_common(dentry, flags, true); +} + +static const struct dentry_operations ovl_dentry_operations = { + .d_real = ovl_d_real, + .d_revalidate = ovl_dentry_revalidate, + .d_weak_revalidate = ovl_dentry_weak_revalidate, +}; + +static struct kmem_cache *ovl_inode_cachep; + +static struct inode *ovl_alloc_inode(struct super_block *sb) +{ + struct ovl_inode *oi = alloc_inode_sb(sb, ovl_inode_cachep, GFP_KERNEL); + + if (!oi) + return NULL; + + oi->cache = NULL; + oi->redirect = NULL; + oi->version = 0; + oi->flags = 0; + oi->__upperdentry = NULL; + oi->lowerdata_redirect = NULL; + oi->oe = NULL; + mutex_init(&oi->lock); + + return &oi->vfs_inode; +} + +static void ovl_free_inode(struct inode *inode) +{ + struct ovl_inode *oi = OVL_I(inode); + + kfree(oi->redirect); + kfree(oi->oe); + mutex_destroy(&oi->lock); + kmem_cache_free(ovl_inode_cachep, oi); +} + +static void ovl_destroy_inode(struct inode *inode) +{ + struct ovl_inode *oi = OVL_I(inode); + + dput(oi->__upperdentry); + ovl_stack_put(ovl_lowerstack(oi->oe), ovl_numlower(oi->oe)); + if (S_ISDIR(inode->i_mode)) + ovl_dir_cache_free(inode); + else + kfree(oi->lowerdata_redirect); +} + +static void ovl_put_super(struct super_block *sb) +{ + struct ovl_fs *ofs = OVL_FS(sb); + + if (ofs) + ovl_free_fs(ofs); +} + +/* Sync real dirty inodes in upper filesystem (if it exists) */ +static int ovl_sync_fs(struct super_block *sb, int wait) +{ + struct ovl_fs *ofs = OVL_FS(sb); + struct super_block *upper_sb; + int ret; + + ret = ovl_sync_status(ofs); + /* + * We have to always set the err, because the return value isn't + * checked in syncfs, and instead indirectly return an error via + * the sb's writeback errseq, which VFS inspects after this call. + */ + if (ret < 0) { + errseq_set(&sb->s_wb_err, -EIO); + return -EIO; + } + + if (!ret) + return ret; + + /* + * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC). + * All the super blocks will be iterated, including upper_sb. + * + * If this is a syncfs(2) call, then we do need to call + * sync_filesystem() on upper_sb, but enough if we do it when being + * called with wait == 1. + */ + if (!wait) + return 0; + + upper_sb = ovl_upper_mnt(ofs)->mnt_sb; + + down_read(&upper_sb->s_umount); + ret = sync_filesystem(upper_sb); + up_read(&upper_sb->s_umount); + + return ret; +} + +/** + * ovl_statfs + * @dentry: The dentry to query + * @buf: The struct kstatfs to fill in with stats + * + * Get the filesystem statistics. As writes always target the upper layer + * filesystem pass the statfs to the upper filesystem (if it exists) + */ +static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) +{ + struct super_block *sb = dentry->d_sb; + struct ovl_fs *ofs = OVL_FS(sb); + struct dentry *root_dentry = sb->s_root; + struct path path; + int err; + + ovl_path_real(root_dentry, &path); + + err = vfs_statfs(&path, buf); + if (!err) { + buf->f_namelen = ofs->namelen; + buf->f_type = OVERLAYFS_SUPER_MAGIC; + if (ovl_has_fsid(ofs)) + buf->f_fsid = uuid_to_fsid(sb->s_uuid.b); + } + + return err; +} + +static const struct super_operations ovl_super_operations = { + .alloc_inode = ovl_alloc_inode, + .free_inode = ovl_free_inode, + .destroy_inode = ovl_destroy_inode, + .drop_inode = generic_delete_inode, + .put_super = ovl_put_super, + .sync_fs = ovl_sync_fs, + .statfs = ovl_statfs, + .show_options = ovl_show_options, +}; + +#define OVL_WORKDIR_NAME "work" +#define OVL_INDEXDIR_NAME "index" + +static struct dentry *ovl_workdir_create(struct ovl_fs *ofs, + const char *name, bool persist) +{ + struct inode *dir = ofs->workbasedir->d_inode; + struct vfsmount *mnt = ovl_upper_mnt(ofs); + struct dentry *work; + int err; + bool retried = false; + + inode_lock_nested(dir, I_MUTEX_PARENT); +retry: + work = ovl_lookup_upper(ofs, name, ofs->workbasedir, strlen(name)); + + if (!IS_ERR(work)) { + struct iattr attr = { + .ia_valid = ATTR_MODE, + .ia_mode = S_IFDIR | 0, + }; + + if (work->d_inode) { + err = -EEXIST; + if (retried) + goto out_dput; + + if (persist) + goto out_unlock; + + retried = true; + err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0); + dput(work); + if (err == -EINVAL) { + work = ERR_PTR(err); + goto out_unlock; + } + goto retry; + } + + err = ovl_mkdir_real(ofs, dir, &work, attr.ia_mode); + if (err) + goto out_dput; + + /* Weird filesystem returning with hashed negative (kernfs)? */ + err = -EINVAL; + if (d_really_is_negative(work)) + goto out_dput; + + /* + * Try to remove POSIX ACL xattrs from workdir. We are good if: + * + * a) success (there was a POSIX ACL xattr and was removed) + * b) -ENODATA (there was no POSIX ACL xattr) + * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported) + * + * There are various other error values that could effectively + * mean that the xattr doesn't exist (e.g. -ERANGE is returned + * if the xattr name is too long), but the set of filesystems + * allowed as upper are limited to "normal" ones, where checking + * for the above two errors is sufficient. + */ + err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_DEFAULT); + if (err && err != -ENODATA && err != -EOPNOTSUPP) + goto out_dput; + + err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_ACCESS); + if (err && err != -ENODATA && err != -EOPNOTSUPP) + goto out_dput; + + /* Clear any inherited mode bits */ + inode_lock(work->d_inode); + err = ovl_do_notify_change(ofs, work, &attr); + inode_unlock(work->d_inode); + if (err) + goto out_dput; + } else { + err = PTR_ERR(work); + goto out_err; + } +out_unlock: + inode_unlock(dir); + return work; + +out_dput: + dput(work); +out_err: + pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n", + ofs->config.workdir, name, -err); + work = NULL; + goto out_unlock; +} + +static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs, + const char *name) +{ + struct kstatfs statfs; + int err = vfs_statfs(path, &statfs); + + if (err) + pr_err("statfs failed on '%s'\n", name); + else + ofs->namelen = max(ofs->namelen, statfs.f_namelen); + + return err; +} + +static int ovl_lower_dir(const char *name, struct path *path, + struct ovl_fs *ofs, int *stack_depth) +{ + int fh_type; + int err; + + err = ovl_check_namelen(path, ofs, name); + if (err) + return err; + + *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth); + + /* + * The inodes index feature and NFS export need to encode and decode + * file handles, so they require that all layers support them. + */ + fh_type = ovl_can_decode_fh(path->dentry->d_sb); + if ((ofs->config.nfs_export || + (ofs->config.index && ofs->config.upperdir)) && !fh_type) { + ofs->config.index = false; + ofs->config.nfs_export = false; + pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n", + name); + } + ofs->nofh |= !fh_type; + /* + * Decoding origin file handle is required for persistent st_ino. + * Without persistent st_ino, xino=auto falls back to xino=off. + */ + if (ofs->config.xino == OVL_XINO_AUTO && + ofs->config.upperdir && !fh_type) { + ofs->config.xino = OVL_XINO_OFF; + pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n", + name); + } + + /* Check if lower fs has 32bit inode numbers */ + if (fh_type != FILEID_INO32_GEN) + ofs->xino_mode = -1; + + return 0; +} + +/* Workdir should not be subdir of upperdir and vice versa */ +static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) +{ + bool ok = false; + + if (workdir != upperdir) { + ok = (lock_rename(workdir, upperdir) == NULL); + unlock_rename(workdir, upperdir); + } + return ok; +} + +static int ovl_own_xattr_get(const struct xattr_handler *handler, + struct dentry *dentry, struct inode *inode, + const char *name, void *buffer, size_t size) +{ + return -EOPNOTSUPP; +} + +static int ovl_own_xattr_set(const struct xattr_handler *handler, + struct mnt_idmap *idmap, + struct dentry *dentry, struct inode *inode, + const char *name, const void *value, + size_t size, int flags) +{ + return -EOPNOTSUPP; +} + +static int ovl_other_xattr_get(const struct xattr_handler *handler, + struct dentry *dentry, struct inode *inode, + const char *name, void *buffer, size_t size) +{ + return ovl_xattr_get(dentry, inode, name, buffer, size); +} + +static int ovl_other_xattr_set(const struct xattr_handler *handler, + struct mnt_idmap *idmap, + struct dentry *dentry, struct inode *inode, + const char *name, const void *value, + size_t size, int flags) +{ + return ovl_xattr_set(dentry, inode, name, value, size, flags); +} + +static const struct xattr_handler ovl_own_trusted_xattr_handler = { + .prefix = OVL_XATTR_TRUSTED_PREFIX, + .get = ovl_own_xattr_get, + .set = ovl_own_xattr_set, +}; + +static const struct xattr_handler ovl_own_user_xattr_handler = { + .prefix = OVL_XATTR_USER_PREFIX, + .get = ovl_own_xattr_get, + .set = ovl_own_xattr_set, +}; + +static const struct xattr_handler ovl_other_xattr_handler = { + .prefix = "", /* catch all */ + .get = ovl_other_xattr_get, + .set = ovl_other_xattr_set, +}; + +static const struct xattr_handler *ovl_trusted_xattr_handlers[] = { + &ovl_own_trusted_xattr_handler, + &ovl_other_xattr_handler, + NULL +}; + +static const struct xattr_handler *ovl_user_xattr_handlers[] = { + &ovl_own_user_xattr_handler, + &ovl_other_xattr_handler, + NULL +}; + +static int ovl_setup_trap(struct super_block *sb, struct dentry *dir, + struct inode **ptrap, const char *name) +{ + struct inode *trap; + int err; + + trap = ovl_get_trap_inode(sb, dir); + err = PTR_ERR_OR_ZERO(trap); + if (err) { + if (err == -ELOOP) + pr_err("conflicting %s path\n", name); + return err; + } + + *ptrap = trap; + return 0; +} + +/* + * Determine how we treat concurrent use of upperdir/workdir based on the + * index feature. This is papering over mount leaks of container runtimes, + * for example, an old overlay mount is leaked and now its upperdir is + * attempted to be used as a lower layer in a new overlay mount. + */ +static int ovl_report_in_use(struct ovl_fs *ofs, const char *name) +{ + if (ofs->config.index) { + pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n", + name); + return -EBUSY; + } else { + pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n", + name); + return 0; + } +} + +static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs, + struct ovl_layer *upper_layer, + const struct path *upperpath) +{ + struct vfsmount *upper_mnt; + int err; + + /* Upperdir path should not be r/o */ + if (__mnt_is_readonly(upperpath->mnt)) { + pr_err("upper fs is r/o, try multi-lower layers mount\n"); + err = -EINVAL; + goto out; + } + + err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir); + if (err) + goto out; + + err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap, + "upperdir"); + if (err) + goto out; + + upper_mnt = clone_private_mount(upperpath); + err = PTR_ERR(upper_mnt); + if (IS_ERR(upper_mnt)) { + pr_err("failed to clone upperpath\n"); + goto out; + } + + /* Don't inherit atime flags */ + upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME); + upper_layer->mnt = upper_mnt; + upper_layer->idx = 0; + upper_layer->fsid = 0; + + /* + * Inherit SB_NOSEC flag from upperdir. + * + * This optimization changes behavior when a security related attribute + * (suid/sgid/security.*) is changed on an underlying layer. This is + * okay because we don't yet have guarantees in that case, but it will + * need careful treatment once we want to honour changes to underlying + * filesystems. + */ + if (upper_mnt->mnt_sb->s_flags & SB_NOSEC) + sb->s_flags |= SB_NOSEC; + + if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) { + ofs->upperdir_locked = true; + } else { + err = ovl_report_in_use(ofs, "upperdir"); + if (err) + goto out; + } + + err = 0; +out: + return err; +} + +/* + * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and + * negative values if error is encountered. + */ +static int ovl_check_rename_whiteout(struct ovl_fs *ofs) +{ + struct dentry *workdir = ofs->workdir; + struct inode *dir = d_inode(workdir); + struct dentry *temp; + struct dentry *dest; + struct dentry *whiteout; + struct name_snapshot name; + int err; + + inode_lock_nested(dir, I_MUTEX_PARENT); + + temp = ovl_create_temp(ofs, workdir, OVL_CATTR(S_IFREG | 0)); + err = PTR_ERR(temp); + if (IS_ERR(temp)) + goto out_unlock; + + dest = ovl_lookup_temp(ofs, workdir); + err = PTR_ERR(dest); + if (IS_ERR(dest)) { + dput(temp); + goto out_unlock; + } + + /* Name is inline and stable - using snapshot as a copy helper */ + take_dentry_name_snapshot(&name, temp); + err = ovl_do_rename(ofs, dir, temp, dir, dest, RENAME_WHITEOUT); + if (err) { + if (err == -EINVAL) + err = 0; + goto cleanup_temp; + } + + whiteout = ovl_lookup_upper(ofs, name.name.name, workdir, name.name.len); + err = PTR_ERR(whiteout); + if (IS_ERR(whiteout)) + goto cleanup_temp; + + err = ovl_is_whiteout(whiteout); + + /* Best effort cleanup of whiteout and temp file */ + if (err) + ovl_cleanup(ofs, dir, whiteout); + dput(whiteout); + +cleanup_temp: + ovl_cleanup(ofs, dir, temp); + release_dentry_name_snapshot(&name); + dput(temp); + dput(dest); + +out_unlock: + inode_unlock(dir); + + return err; +} + +static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs, + struct dentry *parent, + const char *name, umode_t mode) +{ + size_t len = strlen(name); + struct dentry *child; + + inode_lock_nested(parent->d_inode, I_MUTEX_PARENT); + child = ovl_lookup_upper(ofs, name, parent, len); + if (!IS_ERR(child) && !child->d_inode) + child = ovl_create_real(ofs, parent->d_inode, child, + OVL_CATTR(mode)); + inode_unlock(parent->d_inode); + dput(parent); + + return child; +} + +/* + * Creates $workdir/work/incompat/volatile/dirty file if it is not already + * present. + */ +static int ovl_create_volatile_dirty(struct ovl_fs *ofs) +{ + unsigned int ctr; + struct dentry *d = dget(ofs->workbasedir); + static const char *const volatile_path[] = { + OVL_WORKDIR_NAME, "incompat", "volatile", "dirty" + }; + const char *const *name = volatile_path; + + for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) { + d = ovl_lookup_or_create(ofs, d, *name, ctr > 1 ? S_IFDIR : S_IFREG); + if (IS_ERR(d)) + return PTR_ERR(d); + } + dput(d); + return 0; +} + +static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs, + const struct path *workpath) +{ + struct vfsmount *mnt = ovl_upper_mnt(ofs); + struct dentry *workdir; + struct file *tmpfile; + bool rename_whiteout; + bool d_type; + int fh_type; + int err; + + err = mnt_want_write(mnt); + if (err) + return err; + + workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false); + err = PTR_ERR(workdir); + if (IS_ERR_OR_NULL(workdir)) + goto out; + + ofs->workdir = workdir; + + err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir"); + if (err) + goto out; + + /* + * Upper should support d_type, else whiteouts are visible. Given + * workdir and upper are on same fs, we can do iterate_dir() on + * workdir. This check requires successful creation of workdir in + * previous step. + */ + err = ovl_check_d_type_supported(workpath); + if (err < 0) + goto out; + + d_type = err; + if (!d_type) + pr_warn("upper fs needs to support d_type.\n"); + + /* Check if upper/work fs supports O_TMPFILE */ + tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0); + ofs->tmpfile = !IS_ERR(tmpfile); + if (ofs->tmpfile) + fput(tmpfile); + else + pr_warn("upper fs does not support tmpfile.\n"); + + + /* Check if upper/work fs supports RENAME_WHITEOUT */ + err = ovl_check_rename_whiteout(ofs); + if (err < 0) + goto out; + + rename_whiteout = err; + if (!rename_whiteout) + pr_warn("upper fs does not support RENAME_WHITEOUT.\n"); + + /* + * Check if upper/work fs supports (trusted|user).overlay.* xattr + */ + err = ovl_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1); + if (err) { + pr_warn("failed to set xattr on upper\n"); + ofs->noxattr = true; + if (ovl_redirect_follow(ofs)) { + ofs->config.redirect_mode = OVL_REDIRECT_NOFOLLOW; + pr_warn("...falling back to redirect_dir=nofollow.\n"); + } + if (ofs->config.metacopy) { + ofs->config.metacopy = false; + pr_warn("...falling back to metacopy=off.\n"); + } + if (ofs->config.index) { + ofs->config.index = false; + pr_warn("...falling back to index=off.\n"); + } + if (ovl_has_fsid(ofs)) { + ofs->config.uuid = OVL_UUID_NULL; + pr_warn("...falling back to uuid=null.\n"); + } + /* + * xattr support is required for persistent st_ino. + * Without persistent st_ino, xino=auto falls back to xino=off. + */ + if (ofs->config.xino == OVL_XINO_AUTO) { + ofs->config.xino = OVL_XINO_OFF; + pr_warn("...falling back to xino=off.\n"); + } + if (err == -EPERM && !ofs->config.userxattr) + pr_info("try mounting with 'userxattr' option\n"); + err = 0; + } else { + ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE); + } + + /* + * We allowed sub-optimal upper fs configuration and don't want to break + * users over kernel upgrade, but we never allowed remote upper fs, so + * we can enforce strict requirements for remote upper fs. + */ + if (ovl_dentry_remote(ofs->workdir) && + (!d_type || !rename_whiteout || ofs->noxattr)) { + pr_err("upper fs missing required features.\n"); + err = -EINVAL; + goto out; + } + + /* + * For volatile mount, create a incompat/volatile/dirty file to keep + * track of it. + */ + if (ofs->config.ovl_volatile) { + err = ovl_create_volatile_dirty(ofs); + if (err < 0) { + pr_err("Failed to create volatile/dirty file.\n"); + goto out; + } + } + + /* Check if upper/work fs supports file handles */ + fh_type = ovl_can_decode_fh(ofs->workdir->d_sb); + if (ofs->config.index && !fh_type) { + ofs->config.index = false; + pr_warn("upper fs does not support file handles, falling back to index=off.\n"); + } + ofs->nofh |= !fh_type; + + /* Check if upper fs has 32bit inode numbers */ + if (fh_type != FILEID_INO32_GEN) + ofs->xino_mode = -1; + + /* NFS export of r/w mount depends on index */ + if (ofs->config.nfs_export && !ofs->config.index) { + pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n"); + ofs->config.nfs_export = false; + } +out: + mnt_drop_write(mnt); + return err; +} + +static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs, + const struct path *upperpath, + const struct path *workpath) +{ + int err; + + err = -EINVAL; + if (upperpath->mnt != workpath->mnt) { + pr_err("workdir and upperdir must reside under the same mount\n"); + return err; + } + if (!ovl_workdir_ok(workpath->dentry, upperpath->dentry)) { + pr_err("workdir and upperdir must be separate subtrees\n"); + return err; + } + + ofs->workbasedir = dget(workpath->dentry); + + if (ovl_inuse_trylock(ofs->workbasedir)) { + ofs->workdir_locked = true; + } else { + err = ovl_report_in_use(ofs, "workdir"); + if (err) + return err; + } + + err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap, + "workdir"); + if (err) + return err; + + return ovl_make_workdir(sb, ofs, workpath); +} + +static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs, + struct ovl_entry *oe, const struct path *upperpath) +{ + struct vfsmount *mnt = ovl_upper_mnt(ofs); + struct dentry *indexdir; + int err; + + err = mnt_want_write(mnt); + if (err) + return err; + + /* Verify lower root is upper root origin */ + err = ovl_verify_origin(ofs, upperpath->dentry, + ovl_lowerstack(oe)->dentry, true); + if (err) { + pr_err("failed to verify upper root origin\n"); + goto out; + } + + /* index dir will act also as workdir */ + iput(ofs->workdir_trap); + ofs->workdir_trap = NULL; + dput(ofs->workdir); + ofs->workdir = NULL; + indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true); + if (IS_ERR(indexdir)) { + err = PTR_ERR(indexdir); + } else if (indexdir) { + ofs->indexdir = indexdir; + ofs->workdir = dget(indexdir); + + err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap, + "indexdir"); + if (err) + goto out; + + /* + * Verify upper root is exclusively associated with index dir. + * Older kernels stored upper fh in ".overlay.origin" + * xattr. If that xattr exists, verify that it is a match to + * upper dir file handle. In any case, verify or set xattr + * ".overlay.upper" to indicate that index may have + * directory entries. + */ + if (ovl_check_origin_xattr(ofs, ofs->indexdir)) { + err = ovl_verify_set_fh(ofs, ofs->indexdir, + OVL_XATTR_ORIGIN, + upperpath->dentry, true, false); + if (err) + pr_err("failed to verify index dir 'origin' xattr\n"); + } + err = ovl_verify_upper(ofs, ofs->indexdir, upperpath->dentry, + true); + if (err) + pr_err("failed to verify index dir 'upper' xattr\n"); + + /* Cleanup bad/stale/orphan index entries */ + if (!err) + err = ovl_indexdir_cleanup(ofs); + } + if (err || !ofs->indexdir) + pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n"); + +out: + mnt_drop_write(mnt); + return err; +} + +static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) +{ + unsigned int i; + + if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs)) + return true; + + /* + * We allow using single lower with null uuid for index and nfs_export + * for example to support those features with single lower squashfs. + * To avoid regressions in setups of overlay with re-formatted lower + * squashfs, do not allow decoding origin with lower null uuid unless + * user opted-in to one of the new features that require following the + * lower inode of non-dir upper. + */ + if (ovl_allow_offline_changes(ofs) && uuid_is_null(uuid)) + return false; + + for (i = 0; i < ofs->numfs; i++) { + /* + * We use uuid to associate an overlay lower file handle with a + * lower layer, so we can accept lower fs with null uuid as long + * as all lower layers with null uuid are on the same fs. + * if we detect multiple lower fs with the same uuid, we + * disable lower file handle decoding on all of them. + */ + if (ofs->fs[i].is_lower && + uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) { + ofs->fs[i].bad_uuid = true; + return false; + } + } + return true; +} + +/* Get a unique fsid for the layer */ +static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) +{ + struct super_block *sb = path->mnt->mnt_sb; + unsigned int i; + dev_t dev; + int err; + bool bad_uuid = false; + bool warn = false; + + for (i = 0; i < ofs->numfs; i++) { + if (ofs->fs[i].sb == sb) + return i; + } + + if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { + bad_uuid = true; + if (ofs->config.xino == OVL_XINO_AUTO) { + ofs->config.xino = OVL_XINO_OFF; + warn = true; + } + if (ofs->config.index || ofs->config.nfs_export) { + ofs->config.index = false; + ofs->config.nfs_export = false; + warn = true; + } + if (warn) { + pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n", + uuid_is_null(&sb->s_uuid) ? "null" : + "conflicting", + path->dentry, ovl_xino_mode(&ofs->config)); + } + } + + err = get_anon_bdev(&dev); + if (err) { + pr_err("failed to get anonymous bdev for lowerpath\n"); + return err; + } + + ofs->fs[ofs->numfs].sb = sb; + ofs->fs[ofs->numfs].pseudo_dev = dev; + ofs->fs[ofs->numfs].bad_uuid = bad_uuid; + + return ofs->numfs++; +} + +/* + * The fsid after the last lower fsid is used for the data layers. + * It is a "null fs" with a null sb, null uuid, and no pseudo dev. + */ +static int ovl_get_data_fsid(struct ovl_fs *ofs) +{ + return ofs->numfs; +} + + +static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, + struct ovl_fs_context *ctx, struct ovl_layer *layers) +{ + int err; + unsigned int i; + size_t nr_merged_lower; + + ofs->fs = kcalloc(ctx->nr + 2, sizeof(struct ovl_sb), GFP_KERNEL); + if (ofs->fs == NULL) + return -ENOMEM; + + /* + * idx/fsid 0 are reserved for upper fs even with lower only overlay + * and the last fsid is reserved for "null fs" of the data layers. + */ + ofs->numfs++; + + /* + * All lower layers that share the same fs as upper layer, use the same + * pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower + * only overlay to simplify ovl_fs_free(). + * is_lower will be set if upper fs is shared with a lower layer. + */ + err = get_anon_bdev(&ofs->fs[0].pseudo_dev); + if (err) { + pr_err("failed to get anonymous bdev for upper fs\n"); + return err; + } + + if (ovl_upper_mnt(ofs)) { + ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb; + ofs->fs[0].is_lower = false; + } + + nr_merged_lower = ctx->nr - ctx->nr_data; + for (i = 0; i < ctx->nr; i++) { + struct ovl_fs_context_layer *l = &ctx->lower[i]; + struct vfsmount *mnt; + struct inode *trap; + int fsid; + + if (i < nr_merged_lower) + fsid = ovl_get_fsid(ofs, &l->path); + else + fsid = ovl_get_data_fsid(ofs); + if (fsid < 0) + return fsid; + + /* + * Check if lower root conflicts with this overlay layers before + * checking if it is in-use as upperdir/workdir of "another" + * mount, because we do not bother to check in ovl_is_inuse() if + * the upperdir/workdir is in fact in-use by our + * upperdir/workdir. + */ + err = ovl_setup_trap(sb, l->path.dentry, &trap, "lowerdir"); + if (err) + return err; + + if (ovl_is_inuse(l->path.dentry)) { + err = ovl_report_in_use(ofs, "lowerdir"); + if (err) { + iput(trap); + return err; + } + } + + mnt = clone_private_mount(&l->path); + err = PTR_ERR(mnt); + if (IS_ERR(mnt)) { + pr_err("failed to clone lowerpath\n"); + iput(trap); + return err; + } + + /* + * Make lower layers R/O. That way fchmod/fchown on lower file + * will fail instead of modifying lower fs. + */ + mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME; + + layers[ofs->numlayer].trap = trap; + layers[ofs->numlayer].mnt = mnt; + layers[ofs->numlayer].idx = ofs->numlayer; + layers[ofs->numlayer].fsid = fsid; + layers[ofs->numlayer].fs = &ofs->fs[fsid]; + /* Store for printing lowerdir=... in ovl_show_options() */ + ofs->config.lowerdirs[ofs->numlayer] = l->name; + l->name = NULL; + ofs->numlayer++; + ofs->fs[fsid].is_lower = true; + } + + /* + * When all layers on same fs, overlay can use real inode numbers. + * With mount option "xino=<on|auto>", mounter declares that there are + * enough free high bits in underlying fs to hold the unique fsid. + * If overlayfs does encounter underlying inodes using the high xino + * bits reserved for fsid, it emits a warning and uses the original + * inode number or a non persistent inode number allocated from a + * dedicated range. + */ + if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) { + if (ofs->config.xino == OVL_XINO_ON) + pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n"); + ofs->xino_mode = 0; + } else if (ofs->config.xino == OVL_XINO_OFF) { + ofs->xino_mode = -1; + } else if (ofs->xino_mode < 0) { + /* + * This is a roundup of number of bits needed for encoding + * fsid, where fsid 0 is reserved for upper fs (even with + * lower only overlay) +1 extra bit is reserved for the non + * persistent inode number range that is used for resolving + * xino lower bits overflow. + */ + BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30); + ofs->xino_mode = ilog2(ofs->numfs - 1) + 2; + } + + if (ofs->xino_mode > 0) { + pr_info("\"xino\" feature enabled using %d upper inode bits.\n", + ofs->xino_mode); + } + + return 0; +} + +static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, + struct ovl_fs_context *ctx, + struct ovl_fs *ofs, + struct ovl_layer *layers) +{ + int err; + unsigned int i; + size_t nr_merged_lower; + struct ovl_entry *oe; + struct ovl_path *lowerstack; + + struct ovl_fs_context_layer *l; + + if (!ofs->config.upperdir && ctx->nr == 1) { + pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n"); + return ERR_PTR(-EINVAL); + } + + err = -EINVAL; + for (i = 0; i < ctx->nr; i++) { + l = &ctx->lower[i]; + + err = ovl_lower_dir(l->name, &l->path, ofs, &sb->s_stack_depth); + if (err) + return ERR_PTR(err); + } + + err = -EINVAL; + sb->s_stack_depth++; + if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { + pr_err("maximum fs stacking depth exceeded\n"); + return ERR_PTR(err); + } + + err = ovl_get_layers(sb, ofs, ctx, layers); + if (err) + return ERR_PTR(err); + + err = -ENOMEM; + /* Data-only layers are not merged in root directory */ + nr_merged_lower = ctx->nr - ctx->nr_data; + oe = ovl_alloc_entry(nr_merged_lower); + if (!oe) + return ERR_PTR(err); + + lowerstack = ovl_lowerstack(oe); + for (i = 0; i < nr_merged_lower; i++) { + l = &ctx->lower[i]; + lowerstack[i].dentry = dget(l->path.dentry); + lowerstack[i].layer = &ofs->layers[i + 1]; + } + ofs->numdatalayer = ctx->nr_data; + + return oe; +} + +/* + * Check if this layer root is a descendant of: + * - another layer of this overlayfs instance + * - upper/work dir of any overlayfs instance + */ +static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs, + struct dentry *dentry, const char *name, + bool is_lower) +{ + struct dentry *next = dentry, *parent; + int err = 0; + + if (!dentry) + return 0; + + parent = dget_parent(next); + + /* Walk back ancestors to root (inclusive) looking for traps */ + while (!err && parent != next) { + if (is_lower && ovl_lookup_trap_inode(sb, parent)) { + err = -ELOOP; + pr_err("overlapping %s path\n", name); + } else if (ovl_is_inuse(parent)) { + err = ovl_report_in_use(ofs, name); + } + next = parent; + parent = dget_parent(next); + dput(next); + } + + dput(parent); + + return err; +} + +/* + * Check if any of the layers or work dirs overlap. + */ +static int ovl_check_overlapping_layers(struct super_block *sb, + struct ovl_fs *ofs) +{ + int i, err; + + if (ovl_upper_mnt(ofs)) { + err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root, + "upperdir", false); + if (err) + return err; + + /* + * Checking workbasedir avoids hitting ovl_is_inuse(parent) of + * this instance and covers overlapping work and index dirs, + * unless work or index dir have been moved since created inside + * workbasedir. In that case, we already have their traps in + * inode cache and we will catch that case on lookup. + */ + err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir", + false); + if (err) + return err; + } + + for (i = 1; i < ofs->numlayer; i++) { + err = ovl_check_layer(sb, ofs, + ofs->layers[i].mnt->mnt_root, + "lowerdir", true); + if (err) + return err; + } + + return 0; +} + +static struct dentry *ovl_get_root(struct super_block *sb, + struct dentry *upperdentry, + struct ovl_entry *oe) +{ + struct dentry *root; + struct ovl_path *lowerpath = ovl_lowerstack(oe); + unsigned long ino = d_inode(lowerpath->dentry)->i_ino; + int fsid = lowerpath->layer->fsid; + struct ovl_inode_params oip = { + .upperdentry = upperdentry, + .oe = oe, + }; + + root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0)); + if (!root) + return NULL; + + if (upperdentry) { + /* Root inode uses upper st_ino/i_ino */ + ino = d_inode(upperdentry)->i_ino; + fsid = 0; + ovl_dentry_set_upper_alias(root); + if (ovl_is_impuredir(sb, upperdentry)) + ovl_set_flag(OVL_IMPURE, d_inode(root)); + } + + /* Root is always merge -> can have whiteouts */ + ovl_set_flag(OVL_WHITEOUTS, d_inode(root)); + ovl_dentry_set_flag(OVL_E_CONNECTED, root); + ovl_set_upperdata(d_inode(root)); + ovl_inode_init(d_inode(root), &oip, ino, fsid); + ovl_dentry_init_flags(root, upperdentry, oe, DCACHE_OP_WEAK_REVALIDATE); + /* root keeps a reference of upperdentry */ + dget(upperdentry); + + return root; +} + +int ovl_fill_super(struct super_block *sb, struct fs_context *fc) +{ + struct ovl_fs *ofs = sb->s_fs_info; + struct ovl_fs_context *ctx = fc->fs_private; + struct dentry *root_dentry; + struct ovl_entry *oe; + struct ovl_layer *layers; + struct cred *cred; + int err; + + err = -EIO; + if (WARN_ON(fc->user_ns != current_user_ns())) + goto out_err; + + sb->s_d_op = &ovl_dentry_operations; + + err = -ENOMEM; + ofs->creator_cred = cred = prepare_creds(); + if (!cred) + goto out_err; + + err = ovl_fs_params_verify(ctx, &ofs->config); + if (err) + goto out_err; + + err = -EINVAL; + if (ctx->nr == 0) { + if (!(fc->sb_flags & SB_SILENT)) + pr_err("missing 'lowerdir'\n"); + goto out_err; + } + + err = -ENOMEM; + layers = kcalloc(ctx->nr + 1, sizeof(struct ovl_layer), GFP_KERNEL); + if (!layers) + goto out_err; + + ofs->config.lowerdirs = kcalloc(ctx->nr + 1, sizeof(char *), GFP_KERNEL); + if (!ofs->config.lowerdirs) { + kfree(layers); + goto out_err; + } + ofs->layers = layers; + /* + * Layer 0 is reserved for upper even if there's no upper. + * For consistency, config.lowerdirs[0] is NULL. + */ + ofs->numlayer = 1; + + sb->s_stack_depth = 0; + sb->s_maxbytes = MAX_LFS_FILESIZE; + atomic_long_set(&ofs->last_ino, 1); + /* Assume underlying fs uses 32bit inodes unless proven otherwise */ + if (ofs->config.xino != OVL_XINO_OFF) { + ofs->xino_mode = BITS_PER_LONG - 32; + if (!ofs->xino_mode) { + pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n"); + ofs->config.xino = OVL_XINO_OFF; + } + } + + /* alloc/destroy_inode needed for setting up traps in inode cache */ + sb->s_op = &ovl_super_operations; + + if (ofs->config.upperdir) { + struct super_block *upper_sb; + + err = -EINVAL; + if (!ofs->config.workdir) { + pr_err("missing 'workdir'\n"); + goto out_err; + } + + err = ovl_get_upper(sb, ofs, &layers[0], &ctx->upper); + if (err) + goto out_err; + + upper_sb = ovl_upper_mnt(ofs)->mnt_sb; + if (!ovl_should_sync(ofs)) { + ofs->errseq = errseq_sample(&upper_sb->s_wb_err); + if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) { + err = -EIO; + pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n"); + goto out_err; + } + } + + err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work); + if (err) + goto out_err; + + if (!ofs->workdir) + sb->s_flags |= SB_RDONLY; + + sb->s_stack_depth = upper_sb->s_stack_depth; + sb->s_time_gran = upper_sb->s_time_gran; + } + oe = ovl_get_lowerstack(sb, ctx, ofs, layers); + err = PTR_ERR(oe); + if (IS_ERR(oe)) + goto out_err; + + /* If the upper fs is nonexistent, we mark overlayfs r/o too */ + if (!ovl_upper_mnt(ofs)) + sb->s_flags |= SB_RDONLY; + + if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) { + pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n"); + ofs->config.uuid = OVL_UUID_NULL; + } else if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) { + /* Use per instance persistent uuid/fsid */ + ovl_init_uuid_xattr(sb, ofs, &ctx->upper); + } + + if (!ovl_force_readonly(ofs) && ofs->config.index) { + err = ovl_get_indexdir(sb, ofs, oe, &ctx->upper); + if (err) + goto out_free_oe; + + /* Force r/o mount with no index dir */ + if (!ofs->indexdir) + sb->s_flags |= SB_RDONLY; + } + + err = ovl_check_overlapping_layers(sb, ofs); + if (err) + goto out_free_oe; + + /* Show index=off in /proc/mounts for forced r/o mount */ + if (!ofs->indexdir) { + ofs->config.index = false; + if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) { + pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n"); + ofs->config.nfs_export = false; + } + } + + if (ofs->config.metacopy && ofs->config.nfs_export) { + pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n"); + ofs->config.nfs_export = false; + } + + /* + * Support encoding decodable file handles with nfs_export=on + * and encoding non-decodable file handles with nfs_export=off + * if all layers support file handles. + */ + if (ofs->config.nfs_export) + sb->s_export_op = &ovl_export_operations; + else if (!ofs->nofh) + sb->s_export_op = &ovl_export_fid_operations; + + /* Never override disk quota limits or use reserved space */ + cap_lower(cred->cap_effective, CAP_SYS_RESOURCE); + + sb->s_magic = OVERLAYFS_SUPER_MAGIC; + sb->s_xattr = ofs->config.userxattr ? ovl_user_xattr_handlers : + ovl_trusted_xattr_handlers; + sb->s_fs_info = ofs; + sb->s_flags |= SB_POSIXACL; + sb->s_iflags |= SB_I_SKIP_SYNC; + + err = -ENOMEM; + root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe); + if (!root_dentry) + goto out_free_oe; + + sb->s_root = root_dentry; + + return 0; + +out_free_oe: + ovl_free_entry(oe); +out_err: + ovl_free_fs(ofs); + sb->s_fs_info = NULL; + return err; +} + +struct file_system_type ovl_fs_type = { + .owner = THIS_MODULE, + .name = "overlay", + .init_fs_context = ovl_init_fs_context, + .parameters = ovl_parameter_spec, + .fs_flags = FS_USERNS_MOUNT, + .kill_sb = kill_anon_super, +}; +MODULE_ALIAS_FS("overlay"); + +static void ovl_inode_init_once(void *foo) +{ + struct ovl_inode *oi = foo; + + inode_init_once(&oi->vfs_inode); +} + +static int __init ovl_init(void) +{ + int err; + + ovl_inode_cachep = kmem_cache_create("ovl_inode", + sizeof(struct ovl_inode), 0, + (SLAB_RECLAIM_ACCOUNT| + SLAB_MEM_SPREAD|SLAB_ACCOUNT), + ovl_inode_init_once); + if (ovl_inode_cachep == NULL) + return -ENOMEM; + + err = ovl_aio_request_cache_init(); + if (!err) { + err = register_filesystem(&ovl_fs_type); + if (!err) + return 0; + + ovl_aio_request_cache_destroy(); + } + kmem_cache_destroy(ovl_inode_cachep); + + return err; +} + +static void __exit ovl_exit(void) +{ + unregister_filesystem(&ovl_fs_type); + + /* + * Make sure all delayed rcu free inodes are flushed before we + * destroy cache. + */ + rcu_barrier(); + kmem_cache_destroy(ovl_inode_cachep); + ovl_aio_request_cache_destroy(); +} + +module_init(ovl_init); +module_exit(ovl_exit); |