ALSA: usb-audio: Fix potential use-after-free of streams

With the recent full-duplex support of implicit feedback streams, an
endpoint can be still running after closing the capture stream as long
as the playback stream with the sync-endpoint is running.  In such a
state, the URBs are still be handled and they may call retire_data_urb
callback, which tries to transfer the data from the PCM buffer.  Since
the PCM stream gets closed, this may lead to use-after-free.

This patch adds the proper clearance of the callback at stopping the
capture stream for addressing the possible UAF above.

Fixes: 10ce77e4817f ("ALSA: usb-audio: Add duplex sound support for USB devices using implicit feedback")
Link: https://lore.kernel.org/r/20200616120921.12249-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 84c0ae431936ee4996b8c5f97146583146c5aa78..a777d36c4f5a87d88e07cf0f151784d472c875b0 100644 (file)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -1787,6 +1787,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
                return 0;
        case SNDRV_PCM_TRIGGER_STOP:
                stop_endpoints(subs);
+               subs->data_endpoint->retire_data_urb = NULL;
                subs->running = 0;
                return 0;
        case SNDRV_PCM_TRIGGER_PAUSE_PUSH: