CVE-2026-89979 ALSA: pcm: Fix race between non-atomic ops and trigger-start
A race condition in the Linux kernel ALSA PCM subsystem allows concurrent operations to cause state inconsistencies and potential system warnings or crashes.
- 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-2026-89979?
CVE-2026-89979 is a high-severity vulnerability in Linux, published on 16 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:
ALSA: pcm: Fix race between non-atomic ops and trigger-start
We protect the races of the concurrent state transitions between atomic PCM ops, but the checks between the non-atomic ops (hw_params, hw_free and prepare) and the atomic ops aren't perfect; there is a check of the conflicting PCM state at the beginning of hw_params & co, but the atomic PCM ops can be still issued during the non-atomic PCM operations. An example such scenario is that a thread A re-issues the PREPARE or HW_PARAMS for the already prepared stream, while another thread B triggers the PCM start in the middle of the prepare operation. Although this usually doesn't lead to much serious issues, it can give some inconsistency as reported by syzkaller (such as ODEBUG warning).
There are various atomic PCM ops, and basically the only problem is the PCM start as it operates from the PREPARED state. Other trigger commands (stop, etc) are for the running or the other special state, hence they are filtered as pre-condition.
This patch is for preventing the PCM trigger-start during the non- atomic operations in order to address the problems above. Fortunately, the hw_params, hw_free and prepare operations call snd_pcm_buffer_access_lock(), and this can be used for checking the concurrent operations at the PCM trigger -- which sets the runtime->buffer_accessing to a negative (if possible), so the PCM trigger just needs to check the runtime->buffer_accessing value; if it's negative, it means the concurrent non-atomic PCM ops is running.
Which versions are affected by CVE-2026-89979?
How do I fix CVE-2026-89979?
Apply the vendor's patch.
Is CVE-2026-89979 being exploited?
There is no known exploitation of CVE-2026-89979 in the wild and no public exploit code.
Sources
Also known as AZL-101397, BELL-CVE-2026-89979, DEBIAN-CVE-2026-89979, GHSA-r2rw-736q-8cv3, UBUNTU-CVE-2026-89979.