path: root/sound/usb/pcm.c
diff options
authorTakashi Iwai <tiwai@suse.de>2011-02-22 10:21:18 +0100
committerTakashi Iwai <tiwai@suse.de>2011-02-23 08:15:43 +0100
commit382225e62bdb8059b7f915b133426425516dd300 (patch)
tree25f85ecb38145f3ca1547685066b2bf9057e3c72 /sound/usb/pcm.c
parent306496761745942d8167e9193a738b559a7fb0b3 (diff)
ALSA: usb-audio: fix oops due to cleanup race when disconnecting
When a USB audio device is disconnected, snd_usb_audio_disconnect() kills all audio URBs. At the same time, the application, after being notified of the disconnection, might close the device, in which case ALSA calls the .hw_free callback, which should free the URBs too. Commit de1b8b93a0ba "[ALSA] Fix hang-up at disconnection of usb-audio" prevented snd_usb_hw_free() from freeing the URBs to avoid a hang that resulted from this race, but this introduced another race because the URB callbacks could now be executed after snd_usb_hw_free() has returned, and try to access already freed data. Fix the first race by introducing a mutex to serialize the disconnect callback and all PCM callbacks that manage URBs (hw_free and hw_params). Reported-and-tested-by: Pierre-Louis Bossart <pierre-louis.bossart@intel.com> Cc: <stable@kernel.org> [CL: also serialize hw_params callback] Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/usb/pcm.c')
1 files changed, 5 insertions, 2 deletions
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 4132522ac90..e3f680526cb 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -361,6 +361,7 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
if (changed) {
+ mutex_lock(&subs->stream->chip->shutdown_mutex);
/* format changed */
snd_usb_release_substream_urbs(subs, 0);
/* influenced: period_bytes, channels, rate, format, */
@@ -368,6 +369,7 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
snd_pcm_format_physical_width(params_format(hw_params)) *
+ mutex_unlock(&subs->stream->chip->shutdown_mutex);
return ret;
@@ -385,8 +387,9 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
subs->cur_audiofmt = NULL;
subs->cur_rate = 0;
subs->period_bytes = 0;
- if (!subs->stream->chip->shutdown)
- snd_usb_release_substream_urbs(subs, 0);
+ mutex_lock(&subs->stream->chip->shutdown_mutex);
+ snd_usb_release_substream_urbs(subs, 0);
+ mutex_unlock(&subs->stream->chip->shutdown_mutex);
return snd_pcm_lib_free_vmalloc_buffer(substream);