Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: aloop: Fix peer runtime UAF during format-change stop loopback_check_format() may stop the capture side when playback starts with parameters that no longer match a running capture stream. Commit 826af7fa62e3 ("ALSA: aloop: Fix racy access at PCM trigger") moved the peer lookup under cable->lock, but the actual snd_pcm_stop() still runs after dropping that lock. A concurrent close can clear the capture entry from cable->streams[] and detach or free its runtime while the playback trigger path still holds a stale peer substream pointer. Keep a per-cable count of in-flight peer stops before dropping cable->lock, and make free_cable() wait for those stops before detaching the runtime. This preserves the existing behavior while making the peer runtime lifetime explicit.

References 6

• git.kernel.org https://git.kernel.org/stable/c/03f52a9c170431e8f10e156b9dc0dae80b3e9198
• git.kernel.org https://git.kernel.org/stable/c/345c24b2bcf0923dfae1ab41497351c68214ff76
• git.kernel.org https://git.kernel.org/stable/c/5d45e34bf001344e2966dabca1897561bbc9e913
• git.kernel.org https://git.kernel.org/stable/c/83bd62fa9620ac98d5d694bde14c50f98c8e7189
• git.kernel.org https://git.kernel.org/stable/c/bdd9503c3d222d2735b56c7a8b4422ccf3de6e5c
• git.kernel.org https://git.kernel.org/stable/c/e5c33cdc6f402eab8abd36ecf436b22c9d3a8aff

Remediation