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 <eilaimemedsnaimel@gmail.com>
Link: https://patch.msgid.link/20260604142559.3840881-1-eilaimemedsnaimel@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index a541bb235cfa18be15a2256c978d8aa978a57464..302643c1c1921eccff65572d14cc33479df4a592 100644 (file)
--- 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;
                        }
                }