CVE-2026-64112 rbd: eliminate a race in lock_dwork draining on unmap
A race condition in the Linux kernel's RBD driver can cause a kernel assertion failure and crash during image unmap operations.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64112?
CVE-2026-64112 is a high-severity vulnerability in Linux kernel, published on 19 Jul 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:
rbd: eliminate a race in lock_dwork draining on unmap
Given how rbd_lock_add_request() and rbd_img_exclusive_lock() are written, lock_dwork may be (re)queued more than it's actually needed: for example in case a new I/O request comes in while we are in the middle of rbd_acquire_lock() on behalf of another I/O request. This is expected and with rbd_release_lock() preemptively canceling lock_dwork is benign under normal operation.
A more problematic example is maybe_kick_acquire():
if (have_requests || delayed_work_pending(&rbd_dev->lock_dwork)) { dout("%s rbd_dev %p kicking lock_dwork\n", __func__, rbd_dev); mod_delayed_work(rbd_dev->task_wq, &rbd_dev->lock_dwork, 0); }
It's not unrealistic for lock_dwork to get canceled right after delayed_work_pending() returns true and for mod_delayed_work() to requeue it right there anyway. This is a classic TOCTOU race.
When it comes to unmapping the image, there is an implicit assumption of no self-initiated exclusive lock activity past the point of return from rbd_dev_image_unlock() which unlocks the lock if it happens to be held. This unlock is assumed to be final and lock_dwork (as well as all other exclusive lock tasks, really) isn't expected to get queued again. However, lock_dwork is canceled only in cancel_tasks_sync() (i.e. later in the unmap sequence) and on top of that the cancellation can get in effect nullified by maybe_kick_acquire(). This may result in rbd_acquire_lock() executing after rbd_dev_device_release() and rbd_dev_image_release() run and free and/or reset a bunch of things. One of the possible failure modes then is a violated
rbd_assert(rbd_image_format_valid(rbd_dev->image_format));
in rbd_dev_header_info() which is called via rbd_dev_refresh() from rbd_post_acquire_action().
Redo exclusive lock task draining to provide saner semantics and try to meet the assumptions around rbd_dev_image_unlock().
Which versions are affected by CVE-2026-64112?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64112?
Apply the vendor's patch.
Is CVE-2026-64112 being exploited?
There is no known exploitation of CVE-2026-64112 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-92802, BELL-CVE-2026-64112, DEBIAN-CVE-2026-64112, GHSA-559g-j59r-pxg6, ROOT-OS-DEBIAN-11-CVE-2026-64112, ROOT-OS-DEBIAN-12-CVE-2026-64112 and 2 more.