From: paulhsia paulhsia@chromium.org

[ Upstream commit f5cdc9d4003a2f66ea57b3edd3e04acc2b1a4439 ]

If the nullity check for `substream->runtime` is outside of the lock region, it is possible to have a null runtime in the critical section if snd_pcm_detach_substream is called right before the lock.

Signed-off-by: paulhsia paulhsia@chromium.org Link: https://lore.kernel.org/r/20191112171715.128727-2-paulhsia@chromium.org Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- sound/core/pcm_lib.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index 729a85a6211d6..80453266a2def 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1803,11 +1803,14 @@ void snd_pcm_period_elapsed(struct snd_pcm_substream *substream) struct snd_pcm_runtime *runtime; unsigned long flags;

- if (PCM_RUNTIME_CHECK(substream)) + if (snd_BUG_ON(!substream)) return; - runtime = substream->runtime;

snd_pcm_stream_lock_irqsave(substream, flags); + if (PCM_RUNTIME_CHECK(substream)) + goto _unlock; + runtime = substream->runtime; + if (!snd_pcm_running(substream) || snd_pcm_update_hw_ptr0(substream, 1) < 0) goto _end; @@ -1818,6 +1821,7 @@ void snd_pcm_period_elapsed(struct snd_pcm_substream *substream) #endif _end: kill_fasync(&runtime->fasync, SIGIO, POLL_IN); + _unlock: snd_pcm_stream_unlock_irqrestore(substream, flags); } EXPORT_SYMBOL(snd_pcm_period_elapsed);