media: gspca: UBSAN: shift-out-of-bounds in set_flicker

From: Rajeshwar R Shinde <[email protected]>

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 int, a shift-out-of-bounds error occurs. The error is generated when the variable "currentexp" is left-shifted by more than 31 bits. In order to confirm the range is valid, the conditional expression was added.

---
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

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

index 46ed95483e22..dafc522d5e7b 100644
@@ -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 -EINVAL;
 		currentexp = currentexp << sd->params.exposure.gain;
 		sd->params.exposure.gain = 0;
 		/* round down current exposure to nearest value */

2.25.1

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