This is a note to let you know that I've just added the patch titled
ceph: give up on paths longer than PATH_MAX
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ceph-give-up-on-paths-longer-than-path_max.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0df697660c374d5c869d0e72bd6afa776af3dae6
Author: Max Kellermann <max.kellermann@xxxxxxxxx>
Date: Mon Nov 18 23:28:28 2024 +0100
ceph: give up on paths longer than PATH_MAX
[ Upstream commit 550f7ca98ee028a606aa75705a7e77b1bd11720f ]
If the full path to be built by ceph_mdsc_build_path() happens to be
longer than PATH_MAX, then this function will enter an endless (retry)
loop, effectively blocking the whole task. Most of the machine
becomes unusable, making this a very simple and effective DoS
vulnerability.
I cannot imagine why this retry was ever implemented, but it seems
rather useless and harmful to me. Let's remove it and fail with
ENAMETOOLONG instead.
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Dario Weißer <dario@xxxxxxxxx>
Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
Reviewed-by: Alex Markuze <amarkuze@xxxxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 56609b80880c..5ee38dd2c9b9 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2745,12 +2745,11 @@ char *ceph_mdsc_build_path(struct ceph_mds_client *mdsc, struct dentry *dentry,
if (pos < 0) {
/*
- * A rename didn't occur, but somehow we didn't end up where
- * we thought we would. Throw a warning and try again.
+ * The path is longer than PATH_MAX and this function
+ * cannot ever succeed. Creating paths that long is
+ * possible with Ceph, but Linux cannot use them.
*/
- pr_warn_client(cl, "did not end path lookup where expected (pos = %d)\n",
- pos);
- goto retry;
+ return ERR_PTR(-ENAMETOOLONG);
}
*pbase = base;
