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@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/core/pcm_lib.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index f2090025236b..a40a35e51fad 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1906,9 +1906,11 @@ static int wait_for_avail(struct snd_pcm_substream *substream,
if (avail >= runtime->twake)
break;
snd_pcm_stream_unlock_irq(substream);
+ mutex_unlock(&runtime->buffer_mutex);
tout = schedule_timeout(wait_time);
+ mutex_lock(&runtime->buffer_mutex);
snd_pcm_stream_lock_irq(substream);
set_current_state(TASK_INTERRUPTIBLE);
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);
+ mutex_lock(&runtime->buffer_mutex);
snd_pcm_stream_lock_irq(substream);
err = pcm_accessible_state(runtime);
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)
snd_pcm_update_state(substream, runtime);
snd_pcm_stream_unlock_irq(substream);
+ mutex_unlock(&runtime->buffer_mutex);
return xfer > 0 ? (snd_pcm_sframes_t)xfer : err;
}
EXPORT_SYMBOL(__snd_pcm_lib_xfer);
--
2.31.1
