linux-kernel - [PATCH v2] UBSAN: shift-out-of-bounds in set

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Date:   Mon, 21 Aug 2023 13:45:59 +0530
From:   coolrrsh@...il.com
To:     hverkuil@...all.nl, mchehab@...nel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        Rajeshwar R Shinde <coolrrsh@...il.com>,
        syzbot+e27f3dbdab04e43b9f73@...kaller.appspotmail.com
Subject: [PATCH v2] UBSAN: shift-out-of-bounds in set_flicker

From: Rajeshwar R Shinde <coolrrsh@...il.com>

UBSAN: shift-out-of-bounds in drivers/media/usb/gspca/cpia1.c:1031:27
shift exponent 245 is too large for 32-bit type 'int'

shift-out-of-bounds error was triggered when variable 
'sd->params.exposure.gain' is greater than the number of bits of int.
When the variable 'currentexp' is left shifted beyond 31 bits then
the error is produced. Therefore added the conditional expression to 
verify valid range.

Tested via syzbot.

Reported-by: syzbot+e27f3dbdab04e43b9f73@...kaller.appspotmail.com
Closes: https://lore.kernel.org/all/20230818164522.12806-1-
coolrrsh@...il.com/
Link: https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73
Signed-off-by: Rajeshwar R Shinde <coolrrsh@...il.com>

---
v1->v2
changed the patch
changed commit message and tested with checkpatch 

---
 drivers/media/usb/gspca/cpia1.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/usb/gspca/cpia1.c b/drivers/media/usb/gspca/cpia1.c
index 46ed95483e22..dafc522d5e7b 100644
--- a/drivers/media/usb/gspca/cpia1.c
+++ b/drivers/media/usb/gspca/cpia1.c
@@ -1028,6 +1028,8 @@ static int set_flicker(struct gspca_dev *gspca_dev, int on, int apply)
 			sd->params.exposure.expMode = 2;
 			sd->exposure_status = EXPOSURE_NORMAL;
 		}
+		if (sd->params.exposure.gain > 31)
+			return -1;
 		currentexp = currentexp << sd->params.exposure.gain;
 		sd->params.exposure.gain = 0;
 		/* round down current exposure to nearest value */
-- 
2.25.1