media: gspca: cpia1: 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 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 [email protected]

Closes:
https://lore.kernel.org/all/[email protected]

Link https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73

Signed-off-by
<https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73Signed-off-by>:
Rajeshwar R Shinde <[email protected]>
---
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(+)

drivers/media/usb/gspca/cpia1.c +3 -0

index 46ed95483e22..5f5fa851ca64 100644
@@ -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