| From dca947d4d26dbf925a64a6cfb2ddbc035e831a3d Mon Sep 17 00:00:00 2001 |
| From: Takashi Iwai <tiwai@suse.de> |
| Date: Tue, 22 Mar 2022 18:07:18 +0100 |
| Subject: ALSA: pcm: Fix races among concurrent read/write and buffer changes |
| |
| 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 |
| @@ -1906,9 +1906,11 @@ 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) { |
| @@ -2202,6 +2204,7 @@ 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) |
| @@ -2293,6 +2296,7 @@ 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); |
