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Commit 47cef593 authored by Takashi Iwai's avatar Takashi Iwai Committed by Greg Kroah-Hartman
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ALSA: pcm: Fix races among concurrent prepare and hw_params/hw_free calls 



commit 3c3201f8c7bb77eb53b08a3ca8d9a4ddc500b4c0 upstream.

Like the previous fixes to hw_params and hw_free ioctl races, we need
to paper over the concurrent prepare ioctl calls against hw_params and
hw_free, too.

This patch implements the locking with the existing
runtime->buffer_mutex for prepare ioctls.  Unlike the previous case
for snd_pcm_hw_hw_params() and snd_pcm_hw_free(), snd_pcm_prepare() is
performed to the linked streams, hence the lock can't be applied
simply on the top.  For tracking the lock in each linked substream, we
modify snd_pcm_action_group() slightly and apply the buffer_mutex for
the case stream_lock=false (formerly there was no lock applied)
there.

Cc: <stable@vger.kernel.org>
Reviewed-by: default avatarJaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220322170720.3529-4-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
[OP: backport to 4.19: adjusted context]
Signed-off-by: default avatarOvidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b3830197

sound/core/pcm_native.c

+18 −14
Original line number Diff line number Diff line
@@ -1078,15 +1078,17 @@ struct action_ops { 
 */

static int snd_pcm_action_group(const struct action_ops *ops,

				struct snd_pcm_substream *substream,

				int state, int do_lock)

				int state, int stream_lock)

{

	struct snd_pcm_substream *s = NULL;

	struct snd_pcm_substream *s1;

	int res = 0, depth = 1;



	snd_pcm_group_for_each_entry(s, substream) {

		if (do_lock && s != substream) {

			if (s->pcm->nonatomic)

		if (s != substream) {

			if (!stream_lock)

				mutex_lock_nested(&s->runtime->buffer_mutex, depth);

			else if (s->pcm->nonatomic)

				mutex_lock_nested(&s->self_group.mutex, depth);

			else

				spin_lock_nested(&s->self_group.lock, depth);
@@ -1114,11 +1116,12 @@ static int snd_pcm_action_group(const struct action_ops *ops, 
		ops->post_action(s, state);

	}

 _unlock:

	if (do_lock) {

	/* unlock streams */

	snd_pcm_group_for_each_entry(s1, substream) {

		if (s1 != substream) {

				if (s1->pcm->nonatomic)

			if (!stream_lock)

				mutex_unlock(&s1->runtime->buffer_mutex);

			else if (s1->pcm->nonatomic)

				mutex_unlock(&s1->self_group.mutex);

			else

				spin_unlock(&s1->self_group.lock);
@@ -1126,7 +1129,6 @@ static int snd_pcm_action_group(const struct action_ops *ops, 
		if (s1 == s)	/* end */

			break;

	}

	}

	return res;

}
@@ -1206,10 +1208,12 @@ static int snd_pcm_action_nonatomic(const struct action_ops *ops, 
	int res;



	down_read(&snd_pcm_link_rwsem);

	mutex_lock(&substream->runtime->buffer_mutex);

	if (snd_pcm_stream_linked(substream))

		res = snd_pcm_action_group(ops, substream, state, 0);

	else

		res = snd_pcm_action_single(ops, substream, state);

	mutex_unlock(&substream->runtime->buffer_mutex);

	up_read(&snd_pcm_link_rwsem);

	return res;

}