[PATCH 4.4 016/132] ALSA: usb-audio: Fix control access overflow errors from chmap

Greg Kroah-Hartman
2020-12-28T16:50:15Z

From: Takashi Iwai <tiwai@suse.de>

commit c6dde8ffd071aea9d1ce64279178e470977b235c upstream.

The current channel-map control implementation in USB-audio driver may
lead to an error message like
"control 3:0:0:Playback Channel Map:0: access overflow"
when CONFIG_SND_CTL_VALIDATION is set. It's because the chmap get
callback clears the whole array no matter which count is set, and
rather the false-positive detection.

This patch fixes the problem by clearing only the needed array range
at usb_chmap_ctl_get().

Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201211130048.6358-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
sound/usb/stream.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -187,16 +187,16 @@ static int usb_chmap_ctl_get(struct snd_
struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
struct snd_usb_substream *subs = info->private_data;
struct snd_pcm_chmap_elem *chmap = NULL;
- int i;
+ int i = 0;

- memset(ucontrol->value.integer.value, 0,
- sizeof(ucontrol->value.integer.value));
if (subs->cur_audiofmt)
chmap = subs->cur_audiofmt->chmap;
if (chmap) {
for (i = 0; i < chmap->channels; i++)
ucontrol->value.integer.value[i] = chmap->map[i];
}
+ for (; i < subs->channels_max; i++)
+ ucontrol->value.integer.value[i] = 0;
return 0;
}