media: uvcvideo: Silence shift-out-of-bounds warning

[ Upstream commit 171994e ]

UBSAN reports a shift-out-of-bounds warning in uvc_get_le_value(). The
report is correct, but the issue should be harmless as the computed
value isn't used when the shift is negative. This may however cause
incorrect behaviour if a negative shift could generate adverse side
effects (such as a trap on some architectures for instance).

Regardless of whether that may happen or not, silence the warning as a
full WARN backtrace isn't nice.

Reported-by: Bart Van Assche <bvanassche@acm.org>
Fixes: c0efd23 ("V4L/DVB (8145a): USB Video Class driver")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/media/usb/uvc/uvc_ctrl.c

@@ -773,12 +773,16 @@ static s32 uvc_get_le_value(struct uvc_control_mapping *mapping,
 	offset &= 7;
 	mask = ((1LL << bits) - 1) << offset;
 
-	for (; bits > 0; data++) {
+	while (1) {
 		u8 byte = *data & mask;
 		value |= offset > 0 ? (byte >> offset) : (byte << (-offset));
 		bits -= 8 - (offset > 0 ? offset : 0);
+		if (bits <= 0)
+			break;
+
 		offset -= 8;
 		mask = (1 << bits) - 1;
+		data++;
 	}
 
 	/* Sign-extend the value if needed. */