summaryrefslogtreecommitdiffstats
path: root/fs/attr.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/attr.c')
-rw-r--r--fs/attr.c422
1 files changed, 422 insertions, 0 deletions
diff --git a/fs/attr.c b/fs/attr.c
new file mode 100644
index 000000000..fefcdc778
--- /dev/null
+++ b/fs/attr.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/attr.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ * changes by Thomas Schoebel-Theuer
+ */
+
+#include <linux/export.h>
+#include <linux/time.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/sched/signal.h>
+#include <linux/capability.h>
+#include <linux/fsnotify.h>
+#include <linux/fcntl.h>
+#include <linux/security.h>
+#include <linux/evm.h>
+#include <linux/ima.h>
+
+#include "internal.h"
+
+/**
+ * setattr_should_drop_sgid - determine whether the setgid bit needs to be
+ * removed
+ * @inode: inode to check
+ *
+ * This function determines whether the setgid bit needs to be removed.
+ * We retain backwards compatibility and require setgid bit to be removed
+ * unconditionally if S_IXGRP is set. Otherwise we have the exact same
+ * requirements as setattr_prepare() and setattr_copy().
+ *
+ * Return: ATTR_KILL_SGID if setgid bit needs to be removed, 0 otherwise.
+ */
+int setattr_should_drop_sgid(const struct inode *inode)
+{
+ umode_t mode = inode->i_mode;
+
+ if (!(mode & S_ISGID))
+ return 0;
+ if (mode & S_IXGRP)
+ return ATTR_KILL_SGID;
+ if (!in_group_or_capable(inode, inode->i_gid))
+ return ATTR_KILL_SGID;
+ return 0;
+}
+
+/**
+ * setattr_should_drop_suidgid - determine whether the set{g,u}id bit needs to
+ * be dropped
+ * @inode: inode to check
+ *
+ * This function determines whether the set{g,u}id bits need to be removed.
+ * If the setuid bit needs to be removed ATTR_KILL_SUID is returned. If the
+ * setgid bit needs to be removed ATTR_KILL_SGID is returned. If both
+ * set{g,u}id bits need to be removed the corresponding mask of both flags is
+ * returned.
+ *
+ * Return: A mask of ATTR_KILL_S{G,U}ID indicating which - if any - setid bits
+ * to remove, 0 otherwise.
+ */
+int setattr_should_drop_suidgid(struct inode *inode)
+{
+ umode_t mode = inode->i_mode;
+ int kill = 0;
+
+ /* suid always must be killed */
+ if (unlikely(mode & S_ISUID))
+ kill = ATTR_KILL_SUID;
+
+ kill |= setattr_should_drop_sgid(inode);
+
+ if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
+ return kill;
+
+ return 0;
+}
+EXPORT_SYMBOL(setattr_should_drop_suidgid);
+
+static bool chown_ok(const struct inode *inode, kuid_t uid)
+{
+ if (uid_eq(current_fsuid(), inode->i_uid) &&
+ uid_eq(uid, inode->i_uid))
+ return true;
+ if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))
+ return true;
+ if (uid_eq(inode->i_uid, INVALID_UID) &&
+ ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
+ return true;
+ return false;
+}
+
+static bool chgrp_ok(const struct inode *inode, kgid_t gid)
+{
+ if (uid_eq(current_fsuid(), inode->i_uid) &&
+ (in_group_p(gid) || gid_eq(gid, inode->i_gid)))
+ return true;
+ if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))
+ return true;
+ if (gid_eq(inode->i_gid, INVALID_GID) &&
+ ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
+ return true;
+ return false;
+}
+
+/**
+ * setattr_prepare - check if attribute changes to a dentry are allowed
+ * @dentry: dentry to check
+ * @attr: attributes to change
+ *
+ * Check if we are allowed to change the attributes contained in @attr
+ * in the given dentry. This includes the normal unix access permission
+ * checks, as well as checks for rlimits and others. The function also clears
+ * SGID bit from mode if user is not allowed to set it. Also file capabilities
+ * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
+ *
+ * Should be called as the first thing in ->setattr implementations,
+ * possibly after taking additional locks.
+ */
+int setattr_prepare(struct dentry *dentry, struct iattr *attr)
+{
+ struct inode *inode = d_inode(dentry);
+ unsigned int ia_valid = attr->ia_valid;
+
+ /*
+ * First check size constraints. These can't be overriden using
+ * ATTR_FORCE.
+ */
+ if (ia_valid & ATTR_SIZE) {
+ int error = inode_newsize_ok(inode, attr->ia_size);
+ if (error)
+ return error;
+ }
+
+ /* If force is set do it anyway. */
+ if (ia_valid & ATTR_FORCE)
+ goto kill_priv;
+
+ /* Make sure a caller can chown. */
+ if ((ia_valid & ATTR_UID) && !chown_ok(inode, attr->ia_uid))
+ return -EPERM;
+
+ /* Make sure caller can chgrp. */
+ if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid))
+ return -EPERM;
+
+ /* Make sure a caller can chmod. */
+ if (ia_valid & ATTR_MODE) {
+ if (!inode_owner_or_capable(inode))
+ return -EPERM;
+ /* Also check the setgid bit! */
+ if (!in_group_or_capable(inode, (ia_valid & ATTR_GID) ?
+ attr->ia_gid : inode->i_gid))
+ attr->ia_mode &= ~S_ISGID;
+ }
+
+ /* Check for setting the inode time. */
+ if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
+ if (!inode_owner_or_capable(inode))
+ return -EPERM;
+ }
+
+kill_priv:
+ /* User has permission for the change */
+ if (ia_valid & ATTR_KILL_PRIV) {
+ int error;
+
+ error = security_inode_killpriv(dentry);
+ if (error)
+ return error;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(setattr_prepare);
+
+/**
+ * inode_newsize_ok - may this inode be truncated to a given size
+ * @inode: the inode to be truncated
+ * @offset: the new size to assign to the inode
+ *
+ * inode_newsize_ok must be called with i_mutex held.
+ *
+ * inode_newsize_ok will check filesystem limits and ulimits to check that the
+ * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
+ * when necessary. Caller must not proceed with inode size change if failure is
+ * returned. @inode must be a file (not directory), with appropriate
+ * permissions to allow truncate (inode_newsize_ok does NOT check these
+ * conditions).
+ *
+ * Return: 0 on success, -ve errno on failure
+ */
+int inode_newsize_ok(const struct inode *inode, loff_t offset)
+{
+ if (offset < 0)
+ return -EINVAL;
+ if (inode->i_size < offset) {
+ unsigned long limit;
+
+ limit = rlimit(RLIMIT_FSIZE);
+ if (limit != RLIM_INFINITY && offset > limit)
+ goto out_sig;
+ if (offset > inode->i_sb->s_maxbytes)
+ goto out_big;
+ } else {
+ /*
+ * truncation of in-use swapfiles is disallowed - it would
+ * cause subsequent swapout to scribble on the now-freed
+ * blocks.
+ */
+ if (IS_SWAPFILE(inode))
+ return -ETXTBSY;
+ }
+
+ return 0;
+out_sig:
+ send_sig(SIGXFSZ, current, 0);
+out_big:
+ return -EFBIG;
+}
+EXPORT_SYMBOL(inode_newsize_ok);
+
+/**
+ * setattr_copy - copy simple metadata updates into the generic inode
+ * @inode: the inode to be updated
+ * @attr: the new attributes
+ *
+ * setattr_copy must be called with i_mutex held.
+ *
+ * setattr_copy updates the inode's metadata with that specified
+ * in attr. Noticeably missing is inode size update, which is more complex
+ * as it requires pagecache updates.
+ *
+ * The inode is not marked as dirty after this operation. The rationale is
+ * that for "simple" filesystems, the struct inode is the inode storage.
+ * The caller is free to mark the inode dirty afterwards if needed.
+ */
+void setattr_copy(struct inode *inode, const struct iattr *attr)
+{
+ unsigned int ia_valid = attr->ia_valid;
+
+ if (ia_valid & ATTR_UID)
+ inode->i_uid = attr->ia_uid;
+ if (ia_valid & ATTR_GID)
+ inode->i_gid = attr->ia_gid;
+ if (ia_valid & ATTR_ATIME)
+ inode->i_atime = attr->ia_atime;
+ if (ia_valid & ATTR_MTIME)
+ inode->i_mtime = attr->ia_mtime;
+ if (ia_valid & ATTR_CTIME)
+ inode->i_ctime = attr->ia_ctime;
+ if (ia_valid & ATTR_MODE) {
+ umode_t mode = attr->ia_mode;
+ if (!in_group_or_capable(inode, inode->i_gid))
+ mode &= ~S_ISGID;
+ inode->i_mode = mode;
+ }
+}
+EXPORT_SYMBOL(setattr_copy);
+
+/**
+ * notify_change - modify attributes of a filesytem object
+ * @dentry: object affected
+ * @attr: new attributes
+ * @delegated_inode: returns inode, if the inode is delegated
+ *
+ * The caller must hold the i_mutex on the affected object.
+ *
+ * If notify_change discovers a delegation 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. Also, passing NULL is fine for callers holding
+ * the file open for write, as there can be no conflicting delegation in
+ * that case.
+ */
+int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
+{
+ struct inode *inode = dentry->d_inode;
+ umode_t mode = inode->i_mode;
+ int error;
+ struct timespec64 now;
+ unsigned int ia_valid = attr->ia_valid;
+
+ WARN_ON_ONCE(!inode_is_locked(inode));
+
+ if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
+ if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+ return -EPERM;
+ }
+
+ /*
+ * If utimes(2) and friends are called with times == NULL (or both
+ * times are UTIME_NOW), then we need to check for write permission
+ */
+ if (ia_valid & ATTR_TOUCH) {
+ if (IS_IMMUTABLE(inode))
+ return -EPERM;
+
+ if (!inode_owner_or_capable(inode)) {
+ error = inode_permission(inode, MAY_WRITE);
+ if (error)
+ return error;
+ }
+ }
+
+ if ((ia_valid & ATTR_MODE)) {
+ /*
+ * Don't allow changing the mode of symlinks:
+ *
+ * (1) The vfs doesn't take the mode of symlinks into account
+ * during permission checking.
+ * (2) This has never worked correctly. Most major filesystems
+ * did return EOPNOTSUPP due to interactions with POSIX ACLs
+ * but did still updated the mode of the symlink.
+ * This inconsistency led system call wrapper providers such
+ * as libc to block changing the mode of symlinks with
+ * EOPNOTSUPP already.
+ * (3) To even do this in the first place one would have to use
+ * specific file descriptors and quite some effort.
+ */
+ if (S_ISLNK(inode->i_mode))
+ return -EOPNOTSUPP;
+
+ /* Flag setting protected by i_mutex */
+ if (is_sxid(attr->ia_mode))
+ inode->i_flags &= ~S_NOSEC;
+ }
+
+ now = current_time(inode);
+
+ attr->ia_ctime = now;
+ if (!(ia_valid & ATTR_ATIME_SET))
+ attr->ia_atime = now;
+ else
+ attr->ia_atime = timestamp_truncate(attr->ia_atime, inode);
+ if (!(ia_valid & ATTR_MTIME_SET))
+ attr->ia_mtime = now;
+ else
+ attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode);
+
+ if (ia_valid & ATTR_KILL_PRIV) {
+ error = security_inode_need_killpriv(dentry);
+ if (error < 0)
+ return error;
+ if (error == 0)
+ ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
+ }
+
+ /*
+ * We now pass ATTR_KILL_S*ID to the lower level setattr function so
+ * that the function has the ability to reinterpret a mode change
+ * that's due to these bits. This adds an implicit restriction that
+ * no function will ever call notify_change with both ATTR_MODE and
+ * ATTR_KILL_S*ID set.
+ */
+ if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
+ (ia_valid & ATTR_MODE))
+ BUG();
+
+ if (ia_valid & ATTR_KILL_SUID) {
+ if (mode & S_ISUID) {
+ ia_valid = attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode = (inode->i_mode & ~S_ISUID);
+ }
+ }
+ if (ia_valid & ATTR_KILL_SGID) {
+ if (mode & S_ISGID) {
+ if (!(ia_valid & ATTR_MODE)) {
+ ia_valid = attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode = inode->i_mode;
+ }
+ attr->ia_mode &= ~S_ISGID;
+ }
+ }
+ if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
+ return 0;
+
+ /*
+ * Verify that uid/gid changes are valid in the target
+ * namespace of the superblock.
+ */
+ if (ia_valid & ATTR_UID &&
+ !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
+ return -EOVERFLOW;
+ if (ia_valid & ATTR_GID &&
+ !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
+ return -EOVERFLOW;
+
+ /* Don't allow modifications of files with invalid uids or
+ * gids unless those uids & gids are being made valid.
+ */
+ if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
+ return -EOVERFLOW;
+ if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
+ return -EOVERFLOW;
+
+ error = security_inode_setattr(dentry, attr);
+ if (error)
+ return error;
+ error = try_break_deleg(inode, delegated_inode);
+ if (error)
+ return error;
+
+ if (inode->i_op->setattr)
+ error = inode->i_op->setattr(dentry, attr);
+ else
+ error = simple_setattr(dentry, attr);
+
+ if (!error) {
+ fsnotify_change(dentry, ia_valid);
+ ima_inode_post_setattr(dentry);
+ evm_inode_post_setattr(dentry, ia_valid);
+ }
+
+ return error;
+}
+EXPORT_SYMBOL(notify_change);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 10:39:34 +0000