Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 78969700 authored by Takashi Iwai's avatar Takashi Iwai Committed by Greg Kroah-Hartman
Browse files

ALSA: aloop: Fix access to not-yet-ready substream via cable 



commit 8e6b1a72a75bb5067ccb6b56d8ca4aa3a300a64e upstream.

In loopback_open() and loopback_close(), we assign and release the
substream object to the corresponding cable in a racy way.  It's
neither locked nor done in the right position.  The open callback
assigns the substream before its preparation finishes, hence the other
side of the cable may pick it up, which may lead to the invalid memory
access.

This patch addresses these: move the assignment to the end of the open
callback, and wrap with cable->lock for avoiding concurrent accesses.

Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d44f3ad7

sound/drivers/aloop.c

+7 −1
Original line number Diff line number Diff line
@@ -666,7 +666,9 @@ static void free_cable(struct snd_pcm_substream *substream) 
		return;

	if (cable->streams[!substream->stream]) {

		/* other stream is still alive */

		spin_lock_irq(&cable->lock);

		cable->streams[substream->stream] = NULL;

		spin_unlock_irq(&cable->lock);

	} else {

		/* free the cable */

		loopback->cables[substream->number][dev] = NULL;
@@ -706,7 +708,6 @@ static int loopback_open(struct snd_pcm_substream *substream) 
		loopback->cables[substream->number][dev] = cable;

	}

	dpcm->cable = cable;

	cable->streams[substream->stream] = dpcm;



	snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
@@ -738,6 +739,11 @@ static int loopback_open(struct snd_pcm_substream *substream) 
		runtime->hw = loopback_pcm_hardware;

	else

		runtime->hw = cable->hw;



	spin_lock_irq(&cable->lock);

	cable->streams[substream->stream] = dpcm;

	spin_unlock_irq(&cable->lock);



 unlock:

	if (err < 0) {

		free_cable(substream);