Apparently, there are some applications that use IN_DELETE event as an
invalidation mechanism and expect that if they try to open a file with
the name reported with the delete event, that it should not contain the
content of the deleted file.
Commit 49246466a989 ("fsnotify: move fsnotify_nameremove() hook out of
d_delete()") moved the fsnotify delete hook before d_delete() so fsnotify
will have access to a positive dentry.
This allowed a race where opening the deleted file via cached dentry
is now possible after receiving the IN_DELETE event.
To fix the regression, create a new hook fsnotify_delete() that takes
the unlinked inode as an argument and use a helper d_delete_notify() to
pin the inode, so we can pass it to fsnotify_delete() after d_delete().
Backporting hint: this regression is from v5.3. Although patch will
apply with only trivial conflicts to v5.4 and v5.10, it won't build,
because fsnotify_delete() implementation is different in each of those
versions (see fsnotify_link()).
A follow up patch will fix the fsnotify_unlink/rmdir() calls in pseudo
filesystem that do not need to call d_delete().
Reported-by: Ivan Delalande <colona@xxxxxxxxxx>
Link: https://lore.kernel.org/linux-fsdevel/YeNyzoDM5hP5LtGW@visor/
Fixes: 49246466a989 ("fsnotify: move fsnotify_nameremove() hook out of d_delete()")
Cc: stable@xxxxxxxxxxxxxxx # v5.3+
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
Changes since v1:
- Split patch for pseudo filesystem (Jan)
- Fix logic change for DCACHE_NFSFS_RENAMED (Jan)
- btrfs also needs d_delete_notify()
- Make fsnotify_unlink/rmdir() wrappers of fsnotify_delete()
- FS_DELETE event always uses FSNOTIFY_EVENT_INODE data_type
fs/btrfs/ioctl.c | 6 ++---
fs/namei.c | 10 ++++----
include/linux/fsnotify.h | 49 +++++++++++++++++++++++++++++++++++-----
3 files changed, 50 insertions(+), 15 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index edfecfe62b4b..a5ee6ffeadf5 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3060,10 +3060,8 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
btrfs_inode_lock(inode, 0);
err = btrfs_delete_subvolume(dir, dentry);
btrfs_inode_unlock(inode, 0);
- if (!err) {
- fsnotify_rmdir(dir, dentry);
- d_delete(dentry);
- }
+ if (!err)
+ d_delete_notify(dir, dentry);
out_dput:
dput(dentry);
diff --git a/fs/namei.c b/fs/namei.c
index 1f9d2187c765..3c0568d3155b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3973,13 +3973,12 @@ int vfs_rmdir(struct user_namespace *mnt_userns, struct inode *dir,
dentry->d_inode->i_flags |= S_DEAD;
dont_mount(dentry);
detach_mounts(dentry);
- fsnotify_rmdir(dir, dentry);
out:
inode_unlock(dentry->d_inode);
dput(dentry);
if (!error)
- d_delete(dentry);
+ d_delete_notify(dir, dentry);
return error;
}
EXPORT_SYMBOL(vfs_rmdir);
@@ -4101,7 +4100,6 @@ int vfs_unlink(struct user_namespace *mnt_userns, struct inode *dir,
if (!error) {
dont_mount(dentry);
detach_mounts(dentry);
- fsnotify_unlink(dir, dentry);
}
}
}
@@ -4109,9 +4107,11 @@ int vfs_unlink(struct user_namespace *mnt_userns, struct inode *dir,
inode_unlock(target);
/* We don't d_delete() NFS sillyrenamed files--they still exist. */
- if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
+ if (!error && dentry->d_flags & DCACHE_NFSFS_RENAMED) {
+ fsnotify_unlink(dir, dentry);
+ } else if (!error) {
fsnotify_link_count(target);
- d_delete(dentry);
+ d_delete_notify(dir, dentry);
}
return error;
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 3a2d7dc3c607..bb8467cd11ae 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -224,6 +224,43 @@ static inline void fsnotify_link(struct inode *dir, struct inode *inode,
dir, &new_dentry->d_name, 0);
}
+/*
+ * fsnotify_delete - @dentry was unlinked and unhashed
+ *
+ * Caller must make sure that dentry->d_name is stable.
+ *
+ * Note: unlike fsnotify_unlink(), we have to pass also the unlinked inode
+ * as this may be called after d_delete() and old_dentry may be negative.
+ */
+static inline void fsnotify_delete(struct inode *dir, struct inode *inode,
+ struct dentry *dentry)
+{
+ __u32 mask = FS_DELETE;
+
+ if (S_ISDIR(inode->i_mode))
+ mask |= FS_ISDIR;
+
+ fsnotify_name(mask, inode, FSNOTIFY_EVENT_INODE, dir, &dentry->d_name,
+ 0);
+}
+
+/**
+ * d_delete_notify - delete a dentry and call fsnotify_delete()
+ * @dentry: The dentry to delete
+ *
+ * This helper is used to guaranty that the unlinked inode cannot be found
+ * by lookup of this name after fsnotify_delete() event has been delivered.
+ */
+static inline void d_delete_notify(struct inode *dir, struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+
+ ihold(inode);
+ d_delete(dentry);
+ fsnotify_delete(dir, inode, dentry);
+ iput(inode);
+}
+
/*
* fsnotify_unlink - 'name' was unlinked
*
@@ -231,10 +268,10 @@ static inline void fsnotify_link(struct inode *dir, struct inode *inode,
*/
static inline void fsnotify_unlink(struct inode *dir, struct dentry *dentry)
{
- /* Expected to be called before d_delete() */
- WARN_ON_ONCE(d_is_negative(dentry));
+ if (WARN_ON_ONCE(d_is_negative(dentry)))
+ return;
- fsnotify_dirent(dir, dentry, FS_DELETE);
+ fsnotify_delete(dir, d_inode(dentry), dentry);
}
/*
@@ -258,10 +295,10 @@ static inline void fsnotify_mkdir(struct inode *dir, struct dentry *dentry)
*/
static inline void fsnotify_rmdir(struct inode *dir, struct dentry *dentry)
{
- /* Expected to be called before d_delete() */
- WARN_ON_ONCE(d_is_negative(dentry));
+ if (WARN_ON_ONCE(d_is_negative(dentry)))
+ return;
- fsnotify_dirent(dir, dentry, FS_DELETE | FS_ISDIR);
+ fsnotify_delete(dir, d_inode(dentry), dentry);
}
/*
--
2.34.1
