6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Amir Goldstein <amir73il@xxxxxxxxx>
commit 97ac489775f26acfd46a8a60c2f84ce7cc79fa4b upstream.
Commit a95aef69a740 ("fanotify: support reporting non-decodeable file
handles") merged in v6.5-rc1, added the ability to use an fanotify group
with FAN_REPORT_FID mode to watch filesystems that do not support nfs
export, but do know how to encode non-decodeable file handles, with the
newly introduced AT_HANDLE_FID flag.
At the time that this commit was merged, there were no filesystems
in-tree with those traits.
Commit 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles"),
merged in v6.6-rc1, added this trait to overlayfs, thus allowing fanotify
watching of overlayfs with FAN_REPORT_FID mode.
In retrospect, allowing an fanotify filesystem/mount mark on such
filesystem in FAN_REPORT_FID mode will result in getting events with
file handles, without the ability to resolve the filesystem objects from
those file handles (i.e. no open_by_handle_at() support).
For v6.6, the safer option would be to allow this mode for inode marks
only, where the caller has the opportunity to use name_to_handle_at() at
the time of setting the mark. In the future we can revise this decision.
Fixes: a95aef69a740 ("fanotify: support reporting non-decodeable file handles")
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Message-Id: <20231018100000.2453965-2-amir73il@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/notify/fanotify/fanotify_user.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index f69c451018e3..62fe0b679e58 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1585,16 +1585,25 @@ static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)
}
/* Check if filesystem can encode a unique fid */
-static int fanotify_test_fid(struct dentry *dentry)
+static int fanotify_test_fid(struct dentry *dentry, unsigned int flags)
{
+ unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
+ const struct export_operations *nop = dentry->d_sb->s_export_op;
+
+ /*
+ * We need to make sure that the filesystem supports encoding of
+ * file handles so user can use name_to_handle_at() to compare fids
+ * reported with events to the file handle of watched objects.
+ */
+ if (!nop)
+ return -EOPNOTSUPP;
+
/*
- * We need to make sure that the file system supports at least
- * encoding a file handle so user can use name_to_handle_at() to
- * compare fid returned with event to the file handle of watched
- * objects. However, even the relaxed AT_HANDLE_FID flag requires
- * at least empty export_operations for ecoding unique file ids.
+ * For sb/mount mark, we also need to make sure that the filesystem
+ * supports decoding file handles, so user has a way to map back the
+ * reported fids to filesystem objects.
*/
- if (!dentry->d_sb->s_export_op)
+ if (mark_type != FAN_MARK_INODE && !nop->fh_to_dentry)
return -EOPNOTSUPP;
return 0;
@@ -1812,7 +1821,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
if (ret)
goto path_put_and_out;
- ret = fanotify_test_fid(path.dentry);
+ ret = fanotify_test_fid(path.dentry, flags);
if (ret)
goto path_put_and_out;
--
2.42.0
