On Wed, Feb 11, 2026 at 5:29 PM Fabien Sirjean via ceph-users <ceph-users@ceph.io> wrote:
Hello,
We are encountering a reproducible issue with the CephFS kernel client on Ubuntu 24.04 and would appreciate your feedback.
Context: We are preparing an updated Ubuntu 24.04 image for our scientific users. With kernel |6.17.0-14-generic|, the CephFS mount succeeds and the filesystem is visible via |df -h|, but any attempt to access the directory contents (e.g. |ls|) immediately triggers a kernel crash.
From userland, the process is simply killed:
|# ls /net/serdon/illdata Killed|
The mount appears healthy and the filesystem is correctly reported:
|# mount | grep ceph 192.168.170.61,192.168.170.69,192.168.170.70:/ on /net/serdon/illdata type ceph (rw,relatime,name=visa,acl) # df -h | grep serdon 192.168.170.61,192.168.170.69,192.168.170.70:/ 4.1P 2.0P 2.1P 49% /net/serdon/illdata|
However, any access to the mount point triggers a kernel NULL pointer dereference in the Ceph module:
|BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: strcmp+0x10/0x40 Call Trace: ceph_mds_auth_match ceph_mds_check_access ceph_open|
Environment:
|Linux 6.17.0-14-generic #14~24.04.1-Ubuntu CephFS mounted via kernel client (mount -t ceph)|
The issue is fully reproducible: any access to the mount point causes the same kernel crash.
Full stack trace: https://pastebin.com/ZgQHpN0q <https://pastebin.com/ZgQHpN0q>
Questions: - Is this a known issue with the CephFS kernel client on Linux 6.17?
Hi Fabien, Yes, it has just been fixed: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs...
- Does this look like an upstream CephFS bug, or something specific to the Ubuntu 6.17 kernel?
It's an upstream bug; the fix should be trivial to backport to any Ubuntu kernel that is affected. Thanks, Ilya