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ALSA: usb-audio: fix oops due to cleanup race when disconnecting

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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 de1b8b93a0 "[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>
This commit is contained in:
Takashi Iwai 2011-02-22 10:21:18 +01:00
parent 3064967617
commit 382225e62b
3 changed files with 10 additions and 2 deletions
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4
sound/usb/card.c
View File

@ -323,6 +323,7 @@ static int snd_usb_audio_create(struct usb_device *dev, int idx,
return -ENOMEM;
}
mutex_init(&chip->shutdown_mutex);
chip->index = idx;
chip->dev = dev;
chip->card = card;
@ -531,6 +532,7 @@ static void snd_usb_audio_disconnect(struct usb_device *dev, void *ptr)
chip = ptr;
card = chip->card;
mutex_lock(&register_mutex);
mutex_lock(&chip->shutdown_mutex);
chip->shutdown = 1;
chip->num_interfaces--;
if (chip->num_interfaces <= 0) {
@ -548,9 +550,11 @@ static void snd_usb_audio_disconnect(struct usb_device *dev, void *ptr)
snd_usb_mixer_disconnect(p);
}
usb_chip[chip->index] = NULL;
mutex_unlock(&chip->shutdown_mutex);
mutex_unlock(&register_mutex);
snd_card_free_when_closed(card);
} else {
mutex_unlock(&chip->shutdown_mutex);
mutex_unlock(&register_mutex);
}
}

7
sound/usb/pcm.c
View File

@ -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,
params_rate(hw_params),
snd_pcm_format_physical_width(params_format(hw_params)) *
params_channels(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);
}

1
sound/usb/usbaudio.h
View File

@ -36,6 +36,7 @@ struct snd_usb_audio {
struct snd_card *card;
u32 usb_id;
int shutdown;
struct mutex shutdown_mutex;
unsigned int txfr_quirk:1; /* Subframe boundaries on transfers */
int num_interfaces;
int num_suspended_intf;