diff options
| author | Norbert Szetei <norbert@doyensec.com> | 2026-07-28 14:50:01 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2026-07-28 18:29:48 +0200 |
| commit | f495b6c4c8594122918552c9be2b51eb71647cd9 (patch) | |
| tree | b019a725554de291d837160fecf4710ebe908c21 | |
| parent | bed0c8084044364f5ac3f3e89e1bbad423f6b0d4 (diff) | |
ALSA: pcm: wake linked drain waiters on unlink
snd_pcm_drain() on a linked stream parks an on-stack wait entry on the
drained peer's runtime->sleep, and after schedule_timeout() removes it
only if that peer is still found in the caller's group. If group
membership changes during the wait and the sleep ends by signal or
timeout (so autoremove_wake_function() does not run), finish_wait() is
skipped and snd_pcm_drain() returns with the entry still queued on that
stream's sleep list; a later wake_up() then walks a freed stack frame.
This is reachable by unlinking either the drained or the draining stream.
Unlike the close path (snd_pcm_drop() -> snd_pcm_post_stop()),
snd_pcm_unlink() never wakes the sleep queues. Wake every group member
under the group lock before the membership change, so a linked drainer is
released and drops its entry while the streams are still grouped.
The window was opened when snd_pcm_link_rwsem stopped being held across
the wait and the removal became conditional on group membership (see
Fixes). The later switch to finish_wait() kept that conditional removal,
so the signal/timeout case remained.
Fixes: f57f3df03a8e ("ALSA: pcm: More fine-grained PCM link locking")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Link: https://patch.msgid.link/A0705100-D10B-4286-9980-0142ABEEAD51@doyensec.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
| -rw-r--r-- | sound/core/pcm_native.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 7dc0060617f1..c9d0c2bb55b2 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2367,6 +2367,7 @@ static void relink_to_local(struct snd_pcm_substream *substream) static int snd_pcm_unlink(struct snd_pcm_substream *substream) { + struct snd_pcm_substream *s; struct snd_pcm_group *group; bool nonatomic = substream->pcm->nonatomic; bool do_free = false; @@ -2379,6 +2380,12 @@ static int snd_pcm_unlink(struct snd_pcm_substream *substream) group = substream->group; snd_pcm_group_lock_irq(group, nonatomic); + /* release drain waiters before changing membership, else snd_pcm_drain() + * leaves its on-stack wait entry queued on a member's sleep list + */ + snd_pcm_group_for_each_entry(s, substream) + wake_up(&s->runtime->sleep); + relink_to_local(substream); refcount_dec(&group->refs); |