[PATCH v5] media: gspca: cpia1: shift-out-of-bounds in set_flicker

[coolrrsh]

From: Rajeshwar R Shinde <coolrrsh@xxxxxxxxx>

Syzkaller reported the following issue:
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'

When the value of the variable "sd->params.exposure.gain" exceeds the
number of bits in an integer, a shift-out-of-bounds error is reported. It
is triggered because the variable "currentexp" cannot be left-shifted by
more than the number of bits in an integer. In order to avoid invalid
range during left-shift, the conditional expression is added.


Reported-by: syzbot+e27f3dbdab04e43b9f73@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/20230818164522.12806-1-coolrrsh@xxxxxxxxx
Link: https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73
Signed-off-by: Rajeshwar R Shinde <coolrrsh@xxxxxxxxx>
---
v1->v2
Changed the patch. Instead of avoiding shift operation for invalid
input of 'exposure.gain', throw an error for invalid range.
v2->v3
Changed the commit message details
v3->v4
Removed the trailing spaces in commit message
v4->v5
Replaced the hardcoded value with inbuilt macro
---
 drivers/media/usb/gspca/cpia1.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/usb/gspca/cpia1.c b/drivers/media/usb/gspca/cpia1.c
index 46ed95483e22..5f5fa851ca64 100644
--- a/drivers/media/usb/gspca/cpia1.c
+++ b/drivers/media/usb/gspca/cpia1.c
@@ -18,6 +18,7 @@
 
 #include <linux/input.h>
 #include <linux/sched/signal.h>
+#include <linux/bitops.h>
 
 #include "gspca.h"
 
@@ -1028,6 +1029,8 @@ 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 >= BITS_PER_TYPE(currentexp))
+			return -EINVAL;
 		currentexp = currentexp << sd->params.exposure.gain;
 		sd->params.exposure.gain = 0;
 		/* round down current exposure to nearest value */
-- 
2.25.1