ALSA: usb-audio: US16x08: Move overflow check before array access

Buffer overflow could occur in the loop "while", due to accessing an
array element before checking the index.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Daniil Dementev <d.dementev@ispras.ru>
Reviewed-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Link: https://lore.kernel.org/r/20220610165732.2904-1-d.dementev@ispras.ru
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/mixer_us16x08.c b/sound/usb/mixer_us16x08.c
index b7b6f3834ed5e1de4a1b3f897c01bd1117cdbf10..6eb7d93b358d99cdd4d5b6c2d8e587ba725eae10 100644 (file)
--- a/sound/usb/mixer_us16x08.c
+++ b/sound/usb/mixer_us16x08.c
@@ -637,10 +637,10 @@ static int snd_get_meter_comp_index(struct snd_us16x08_meter_store *store)
                }
        } else {
                /* skip channels with no compressor active */
-               while (!store->comp_store->val[
+               while (store->comp_index <= SND_US16X08_MAX_CHANNELS
+                       && !store->comp_store->val[
                        COMP_STORE_IDX(SND_US16X08_ID_COMP_SWITCH)]
-                       [store->comp_index - 1]
-                       && store->comp_index <= SND_US16X08_MAX_CHANNELS) {
+                       [store->comp_index - 1]) {
                        store->comp_index++;
                }
                ret = store->comp_index++;