Commit 66f2d19f authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: pcm: Fix memory leak at closing a stream without hw_free 



ALSA PCM core recently introduced a new managed PCM buffer allocation
mode that does allocate / free automatically at hw_params and
hw_free.  However, it overlooked the code path directly calling
hw_free PCM ops at releasing the PCM substream, and it may result in a
memory leak as spotted by syzkaller when no buffer preallocation is
used (e.g. vmalloc buffer).

This patch papers over it with a slight refactoring.  The hw_free ops
call and relevant tasks are unified in a new helper function, and call
it from both places.

Fixes: 0dba808e ("ALSA: pcm: Introduce managed buffer allocation mode")
Reported-by: default avatar <syzbot+30edd0f34bfcdc548ac4@syzkaller.appspotmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200129195907.12197-1-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 46b770f7

sound/core/pcm_native.c

+15 −9
Original line number Diff line number Diff line
@@ -786,10 +786,22 @@ end: 
	return err;

}



static int do_hw_free(struct snd_pcm_substream *substream)

{

	int result = 0;



	snd_pcm_sync_stop(substream);

	if (substream->ops->hw_free)

		result = substream->ops->hw_free(substream);

	if (substream->managed_buffer_alloc)

		snd_pcm_lib_free_pages(substream);

	return result;

}



static int snd_pcm_hw_free(struct snd_pcm_substream *substream)

{

	struct snd_pcm_runtime *runtime;

	int result = 0;

	int result;



	if (PCM_RUNTIME_CHECK(substream))

		return -ENXIO;
@@ -806,11 +818,7 @@ static int snd_pcm_hw_free(struct snd_pcm_substream *substream) 
	snd_pcm_stream_unlock_irq(substream);

	if (atomic_read(&substream->mmap_count))

		return -EBADFD;

	snd_pcm_sync_stop(substream);

	if (substream->ops->hw_free)

		result = substream->ops->hw_free(substream);

	if (substream->managed_buffer_alloc)

		snd_pcm_lib_free_pages(substream);

	result = do_hw_free(substream);

	snd_pcm_set_state(substream, SNDRV_PCM_STATE_OPEN);

	pm_qos_remove_request(&substream->latency_pm_qos_req);

	return result;
@@ -2529,9 +2537,7 @@ void snd_pcm_release_substream(struct snd_pcm_substream *substream) 


	snd_pcm_drop(substream);

	if (substream->hw_opened) {

		if (substream->ops->hw_free &&

		    substream->runtime->status->state != SNDRV_PCM_STATE_OPEN)

			substream->ops->hw_free(substream);

		do_hw_free(substream);

		substream->ops->close(substream);

		substream->hw_opened = 0;

	}

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