[PATCH v3] media: gspca: UBSAN: shift-out-of-bounds in set_flicker

[PATCH v3] media: gspca: UBSAN: shift-out-of-bounds in set_flicker

[coolrrsh]

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

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.
				
Reported-by: syzbot+e27f3dbdab04e43b9f73@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/20230818164522.12806-1-coolrrsh@gmail.com
Link: https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73
Signed-off-by: Rajeshwar R Shinde <coolrrsh@gmail.com>							
---
v1->v2			
Changed the patch
v2->v3				
Changed the commit message	
---
 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

Re: [PATCH v3] media: gspca: UBSAN: shift-out-of-bounds in set_flicker

[Greg KH]

On Thu, Aug 24, 2023 at 02:27:31PM +0530, coolrrsh@gmail.com wrote:
> From: Rajeshwar R Shinde <coolrrsh@gmail.com>
> 
> 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.
> 				
> Reported-by: syzbot+e27f3dbdab04e43b9f73@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/20230818164522.12806-1-coolrrsh@gmail.com
> Link: https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73
> Signed-off-by: Rajeshwar R Shinde <coolrrsh@gmail.com>							

You have loads of trailing whitespace, please fix your editor to not do
that.

> ---
> v1->v2			
> Changed the patch

In what way?  Be specific.

> v2->v3				
> Changed the commit message	

Again, be specific please.  Otherwise all changes could be listed with
these two sentances and that helps none of us out :(

> ---
>  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;

Why is this still -1?

greg k-h