[PATCH 4.19 128/148] ALSA: usb-audio: Stop parsing channels bits when all channels are found.

Sasha Levin
2024-03-24T23:52:41Z

From: Johan Carlsson <johan.carlsson@teenage.engineering>

[ Upstream commit a39d51ff1f52cd0b6fe7d379ac93bd8b4237d1b7 ]

If a usb audio device sets more bits than the amount of channels
it could write outside of the map array.

Signed-off-by: Johan Carlsson <johan.carlsson@teenage.engineering>
Fixes: 04324ccc75f9 ("ALSA: usb-audio: add channel map support")
Message-ID: <20240313081509.9801-1-johan.carlsson@teenage.engineering>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
sound/usb/stream.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sound/usb/stream.c b/sound/usb/stream.c
index 1cfb30465df7d..3f20438a1b56e 100644
--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -306,9 +306,12 @@ static struct snd_pcm_chmap_elem *convert_chmap(int channels, unsigned int bits,
c = 0;

if (bits) {
- for (; bits && *maps; maps++, bits >>= 1)
+ for (; bits && *maps; maps++, bits >>= 1) {
if (bits & 1)
chmap->map[c++] = *maps;
+ if (c == chmap->channels)
+ break;
+ }
} else {
/* If we're missing wChannelConfig, then guess something
to make sure the channel map is not skipped entirely */
--
2.43.0