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

[Hans Verkuil]

Relax :-) I'll pick it up the next time I go through simple bug fix patches
like this one, probably in 2-3 weeks or so.

Regards,

	Hans

On 02/09/2023 19:56, Rajeshwar Shinde wrote:
> Remainder 
> 
> On Wed, 30 Aug, 2023, 1:14 pm , <coolrrsh@xxxxxxxxx <mailto:coolrrsh@xxxxxxxxx>> wrote:
> 
>     From: Rajeshwar R Shinde <coolrrsh@xxxxxxxxx <mailto: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 <mailto:syzbot%2Be27f3dbdab04e43b9f73@xxxxxxxxxxxxxxxxxxxxxxxxx>
>     Closes: https://lore.kernel.org/all/20230818164522.12806-1-coolrrsh@xxxxxxxxx <https://lore.kernel.org/all/20230818164522.12806-1-coolrrsh@xxxxxxxxx>
>     Link: https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73
>     Signed-off-by <https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73Signed-off-by>: Rajeshwar R Shinde <coolrrsh@xxxxxxxxx <mailto: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
>