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

[ Upstream commit 171994e498 ]

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: c0efd23292 ("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>
5.4-rM2-2.2.x-imx-squashed
Laurent Pinchart 2020-08-19 01:56:49 +02:00 committed by Greg Kroah-Hartman
parent 8504250759
commit 8bcc5c2707
1 changed files with 5 additions and 1 deletions
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6
drivers/media/usb/uvc/uvc_ctrl.c
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@ -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. */