CVE-2026-89979

Status: UPDATED  |  Advisory ID: CVE-2026-89979

Key Details

Affected Products, Subsystems & Sectors

What to Know

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. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References