From: Ji'an Zhou Date: Thu, 4 Jun 2026 14:25:59 +0000 (+0000) Subject: ALSA: PCM: Fix wait queue list corruption in snd_pcm_drain() on linked streams X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=88fe2e3658726cb21ff2dcf9770bf672f9b9d31b;p=thirdparty%2Flinux.git ALSA: PCM: Fix wait queue list corruption in snd_pcm_drain() on linked streams snd_pcm_drain() uses init_waitqueue_entry which does not clear entry.prev/next, and add_wait_queue with a conditional remove_wait_queue that is skipped when to_check is no longer in the group after concurrent UNLINK. The orphaned wait entry remains on the unlinked substream sleep queue. On the next drain iteration, add_wait_queue adds the entry to a new queue while still linked on the old one, corrupting both lists. A subsequent wake_up dereferences NULL at the func pointer (mapped from the spinlock at offset 0 of the misinterpreted wait_queue_head_t), causing a kernel panic. Replace init_waitqueue_entry/add_wait_queue/conditional remove_wait_queue with init_wait_entry/prepare_to_wait/ finish_wait. init_wait_entry clears prev/next via INIT_LIST_HEAD on each iteration and sets autoremove_wake_function which auto-removes the entry on wake-up. finish_wait safely handles both the already-removed and still-queued cases. Fixes: 9b1dbd69ba6f ("ALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain") Signed-off-by: Ji'an Zhou Link: https://patch.msgid.link/20260604142559.3840881-1-eilaimemedsnaimel@gmail.com Signed-off-by: Takashi Iwai --- diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index a541bb235cfa..302643c1c192 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2199,9 +2199,8 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream, drain_no_period_wakeup = to_check->no_period_wakeup; drain_rate = to_check->rate; drain_bufsz = to_check->buffer_size; - init_waitqueue_entry(&wait, current); - set_current_state(TASK_INTERRUPTIBLE); - add_wait_queue(&to_check->sleep, &wait); + init_wait_entry(&wait, 0); + prepare_to_wait(&to_check->sleep, &wait, TASK_INTERRUPTIBLE); snd_pcm_stream_unlock_irq(substream); if (drain_no_period_wakeup) tout = MAX_SCHEDULE_TIMEOUT; @@ -2219,7 +2218,7 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream, group = snd_pcm_stream_group_ref(substream); snd_pcm_group_for_each_entry(s, substream) { if (s->runtime == to_check) { - remove_wait_queue(&to_check->sleep, &wait); + finish_wait(&to_check->sleep, &wait); break; } }