Commit c1f24841 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: usxy2: Fix potential doubly allocations 

The PCM shmem pages are allocated in snd_usx2y_usbpcm_prepare().
Theoretically the prepare callback may be called simultaneously for
both playback and capture, hence this allocation can be racy.

Make sure that the allocation is performed exclusively by extending
the pcm_mutex lock to cover the allocation code, too.

Link: https://lore.kernel.org/r/20210517131545.27252-8-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 02d382af

sound/usb/usx2y/usx2yhwdeppcm.c

+6 −3
Original line number Diff line number Diff line
@@ -503,15 +503,18 @@ static int snd_usx2y_usbpcm_prepare(struct snd_pcm_substream *substream) 


	snd_printdd("snd_usx2y_pcm_prepare(%p)\n", substream);



	mutex_lock(&usx2y->pcm_mutex);



	if (!usx2y->hwdep_pcm_shm) {

		usx2y->hwdep_pcm_shm = alloc_pages_exact(USX2Y_HWDEP_PCM_PAGES,

							 GFP_KERNEL);

		if (!usx2y->hwdep_pcm_shm)

			return -ENOMEM;

		if (!usx2y->hwdep_pcm_shm) {

			err = -ENOMEM;

			goto up_prepare_mutex;

		}

		memset(usx2y->hwdep_pcm_shm, 0, USX2Y_HWDEP_PCM_PAGES);

	}



	mutex_lock(&usx2y->pcm_mutex);

	usx2y_subs_prepare(subs);

	// Start hardware streams

	// SyncStream first....