Commit 31be5425 authored Jan 10, 2013 by Takashi Iwai

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>

parent c18ab0ba

sound/usb/pcm.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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,

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