diff options
| author | Mehul Rao <mehulrao@gmail.com> | 2026-03-05 14:35:07 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-03-19 16:14:59 +0100 |
| commit | c2f64e05a0587a83ec42dbd6b7a7ded79b2ff694 (patch) | |
| tree | bfbe43c7a0ce6b16c4f1e8c1b5c55bc62507ebb4 /sound | |
| parent | 3820d732047cb8b4cbe896a78382e16d25f28b4b (diff) | |
ALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain()
commit 9b1dbd69ba6f8f8c69bc7b77c2ce3b9c6ed05ba6 upstream.
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.
Fixes: f2b3614cefb6 ("ALSA: PCM - Don't check DMA time-out too shortly")
Cc: stable@vger.kernel.org
Signed-off-by: Mehul Rao <mehulrao@gmail.com>
Link: https://patch.msgid.link/20260305193508.311096-1-mehulrao@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound')
| -rw-r--r-- | sound/core/pcm_native.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 0a358d94b17c..495ff93fcd1d 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2144,6 +2144,10 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream, for (;;) { long tout; struct snd_pcm_runtime *to_check; + unsigned int drain_rate; + snd_pcm_uframes_t drain_bufsz; + bool drain_no_period_wakeup; + if (signal_pending(current)) { result = -ERESTARTSYS; break; @@ -2163,16 +2167,25 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream, snd_pcm_group_unref(group, substream); if (!to_check) break; /* all drained */ + /* + * Cache the runtime fields needed after unlock. + * A concurrent close() on the linked stream may free + * its runtime via snd_pcm_detach_substream() once we + * release the stream lock below. + */ + 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); snd_pcm_stream_unlock_irq(substream); - if (runtime->no_period_wakeup) + if (drain_no_period_wakeup) tout = MAX_SCHEDULE_TIMEOUT; else { tout = 100; - if (runtime->rate) { - long t = runtime->buffer_size * 1100 / runtime->rate; + if (drain_rate) { + long t = drain_bufsz * 1100 / drain_rate; tout = max(t, tout); } tout = msecs_to_jiffies(tout); |