From: Takashi Iwai tiwai@suse.de
commit dca947d4d26dbf925a64a6cfb2ddbc035e831a3d upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/core/pcm_lib.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1905,9 +1905,11 @@ static int wait_for_avail(struct snd_pcm 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) { @@ -2201,6 +2203,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(str
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) @@ -2288,6 +2291,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(str 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);