[PATCH 5.3 17/48] ALSA: usb-audio: Fix incorrect size check for processing/extension units

[Greg Kroah-Hartman]

From: Takashi Iwai <tiwai@xxxxxxx>

commit 976a68f06b2ea49e2ab67a5f84919a8b105db8be upstream.

The recently introduced unit descriptor validation had some bug for
processing and extension units, it counts a bControlSize byte twice so
it expected a bigger size than it should have been.  This seems
resulting in a probe error on a few devices.

Fix the calculation for proper checks of PU and EU.

Fixes: 57f8770620e9 ("ALSA: usb-audio: More validations of descriptor units")
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20191114165613.7422-1-tiwai@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/sound/usb/validate.c
+++ b/sound/usb/validate.c
@@ -81,9 +81,9 @@ static bool validate_processing_unit(con
 	switch (v->protocol) {
 	case UAC_VERSION_1:
 	default:
-		/* bNrChannels, wChannelConfig, iChannelNames, bControlSize */
-		len += 1 + 2 + 1 + 1;
-		if (d->bLength < len) /* bControlSize */
+		/* bNrChannels, wChannelConfig, iChannelNames */
+		len += 1 + 2 + 1;
+		if (d->bLength < len + 1) /* bControlSize */
 			return false;
 		m = hdr[len];
 		len += 1 + m + 1; /* bControlSize, bmControls, iProcessing */