CVE-2026-97521 gfs2: fix quota init duplicate scan
A local attacker can cause a kernel crash in the GFS2 filesystem on PREEMPT_RT systems by triggering a sleeping function call in an atomic context.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-97521?
CVE-2026-97521 is a denial of service vulnerability in Linux, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
gfs2: fix quota init duplicate scan
gfs2_quota_init() checks for duplicate quota_change IDs while holding qd_lock and the quota hash bucket bitlock. That path used gfs2_qd_search_bucket(), which takes a lockref reference via lockref_get_not_dead().
On PREEMPT_RT this may sleep, which is not allowed under the bucket bitlock, triggering "sleeping function called from invalid context".
Use a no-ref bucket lookup in this path, then continue duplicate handling without taking a lockref there.
Refactor gfs2_qd_search_bucket() to build on top of the no-ref helper so lookup traversal stays in one place.
This patch fixes a bug reported by syzbot.
Which versions are affected by CVE-2026-97521?
How do I fix CVE-2026-97521?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-97521 being exploited?
There is no known exploitation of CVE-2026-97521 in the wild and no public exploit code.
Sources
Also known as AZL-103757, BELL-CVE-2026-97521, DEBIAN-CVE-2026-97521, GHSA-jgmg-x8vv-p7hr, UBUNTU-CVE-2026-97521.