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[5.4,2/5] ALSA: pcm: Fix races among concurrent read/write and buffer changes

Message ID 20220506091013.1746159-3-ovidiu.panait@windriver.com
State Superseded
Headers show
Series ALSA: pcm: backports for CVE-2022-1048 | expand

Commit Message

Ovidiu Panait May 6, 2022, 9:10 a.m. UTC 
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: Ovidiu Panait <ovidiu.panait@windriver.com>
---
 sound/core/pcm_lib.c | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index fd300c3addde..fdb141e426ac 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1861,9 +1861,11 @@  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) {
@@ -2157,6 +2159,7 @@  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)
@@ -2244,6 +2247,7 @@  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);