From 31be5425d795585251a3ee970319c37643e0cda2 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 10 Jan 2013 14:06:38 +0100
Subject: [PATCH] ALSA: usb-audio: Fix NULL dereference by access to
non-existing substream
The commit [0d9741c0: ALSA: usb-audio: sync ep init fix for
audioformat mismatch] introduced the correction of parameters to be
set for sync EP. But since the new code assumes that the sync EP is
always paired with the data EP of another direction, it triggers Oops
when a device only with a single direction is used.
This patch adds a proper check of sync EP type and the presence of the
paired substream for avoiding the crash.
Reported-and-tested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/usb/pcm.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index c6593101c049..d82e378d37cb 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -511,6 +511,16 @@ static int configure_sync_endpoint(struct snd_usb_substream *subs)
struct snd_usb_substream *sync_subs =
&subs->stream->substream[subs->direction ^ 1];
+ if (subs->sync_endpoint->type != SND_USB_ENDPOINT_TYPE_DATA ||
+ !subs->stream)
+ return snd_usb_endpoint_set_params(subs->sync_endpoint,
+ subs->pcm_format,
+ subs->channels,
+ subs->period_bytes,
+ subs->cur_rate,
+ subs->cur_audiofmt,
+ NULL);
+
/* Try to find the best matching audioformat. */
list_for_each_entry(fp, &sync_subs->fmt_list, list) {
int score = match_endpoint_audioformats(fp, subs->cur_audiofmt,
--
2.20.1