In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain() In the drain loop, the local variable 'runtime' is reassigned to a linked stream's runtime (runtime = s-runtime at line 2157). After releasing the stream lock at line 2169, the code accesses runtime-no_period_wakeup, runtime-rate, and runtime-buffer_size (lines 2170-2178), all referencing the linked stream's runtime without any lock or refcount protecting its lifetime. A concurrent close() on the linked stream's fd triggers snd_pcm_release_substream() - snd_pcm_drop() - pcm_release_private() - snd_pcm_unlink() - snd_pcm_detach_substream() - kfree(runtime).

No synchronization prevents kfree(runtime) from completing while the drain path dereferences the stale pointer. Fix by caching the needed runtime fields (no_period_wakeup, rate, buffer_size) into local variables while still holding the stream lock, and using the cached values after the lock is released.