ALSA: pcm: Fix stream lock usage in snd_pcm_period_elapsed() (f5cdc9d4) · Commits · 戴 / test

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>

sound/core/pcm_lib.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1782,11 +1782,14 @@ 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;
		@@ -1797,6 +1800,7 @@ 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);

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