From 171994e498a0426cbe17f874c5c6af3c0af45200 Mon Sep 17 00:00:00 2001
From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Date: Wed, 19 Aug 2020 01:56:49 +0200
Subject: [PATCH] media: uvcvideo: Silence shift-out-of-bounds warning
Git-commit: 171994e498a0426cbe17f874c5c6af3c0af45200
Patch-mainline: v5.10-rc1
References: git-fixes
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: c0efd232929c ("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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/media/usb/uvc/uvc_ctrl.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 76e4c8859871..f479d8971dfb 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/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. */
--
2.16.4