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ALSA: pcm: Fix races among concurrent read/write and buffer changes

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In the current PCM design, the read/write syscalls (as well as the
equivalent ioctls) are allowed before the PCM stream is running, that
is, at PCM PREPARED state.  Meanwhile, we also allow to re-issue
hw_params and hw_free ioctl calls at the PREPARED state that may
change or free the buffers, too.  The problem is that there is no
protection against those mix-ups.

This patch applies the previously introduced runtime->buffer_mutex to
the read/write operations so that the concurrent hw_params or hw_free
call can no longer interfere during the operation.  The mutex is
unlocked before scheduling, so we don't take it too long.

Cc: <stable@vger.kernel.org>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220322170720.3529-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2022-03-22 18:07:18 +01:00
parent 92ee3c60ec
commit dca947d4d2
1 changed files with 4 additions and 0 deletions
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4
sound/core/pcm_lib.c
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@ -1906,9 +1906,11 @@ static int wait_for_avail(struct snd_pcm_substream *substream,
if (avail >= runtime->twake) if (avail >= runtime->twake)
break; break;
snd_pcm_stream_unlock_irq(substream); snd_pcm_stream_unlock_irq(substream);
mutex_unlock(&runtime->buffer_mutex);
tout = schedule_timeout(wait_time); tout = schedule_timeout(wait_time);
mutex_lock(&runtime->buffer_mutex);
snd_pcm_stream_lock_irq(substream); snd_pcm_stream_lock_irq(substream);
set_current_state(TASK_INTERRUPTIBLE); set_current_state(TASK_INTERRUPTIBLE);
switch (runtime->status->state) { switch (runtime->status->state) {
@ -2219,6 +2221,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
nonblock = !!(substream->f_flags & O_NONBLOCK); nonblock = !!(substream->f_flags & O_NONBLOCK);
mutex_lock(&runtime->buffer_mutex);
snd_pcm_stream_lock_irq(substream); snd_pcm_stream_lock_irq(substream);
err = pcm_accessible_state(runtime); err = pcm_accessible_state(runtime);
if (err < 0) if (err < 0)
@ -2310,6 +2313,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
if (xfer > 0 && err >= 0) if (xfer > 0 && err >= 0)
snd_pcm_update_state(substream, runtime); snd_pcm_update_state(substream, runtime);
snd_pcm_stream_unlock_irq(substream); snd_pcm_stream_unlock_irq(substream);
mutex_unlock(&runtime->buffer_mutex);
return xfer > 0 ? (snd_pcm_sframes_t)xfer : err; return xfer > 0 ? (snd_pcm_sframes_t)xfer : err;
} }
EXPORT_SYMBOL(__snd_pcm_lib_xfer); EXPORT_SYMBOL(__snd_pcm_lib_xfer);