[v2] UBSAN: shift-out-of-bounds in set_flicker

[PATCH v2] UBSAN: shift-out-of-bounds in set_flicker

Posted by coolrrsh@gmail.com 2 years, 3 months ago

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'

shift-out-of-bounds error was triggered when variable 
'sd->params.exposure.gain' is greater than the number of bits of int.
When the variable 'currentexp' is left shifted beyond 31 bits then
the error is produced. Therefore added the conditional expression to 
verify valid range.

Tested via syzbot.

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
changed commit message and tested with checkpatch 

---
 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 v2] UBSAN: shift-out-of-bounds in set_flicker

Posted by Greg KH 2 years, 3 months ago

On Thu, Aug 24, 2023 at 12:36:30PM +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'
> 
> shift-out-of-bounds error was triggered when variable 
> 'sd->params.exposure.gain' is greater than the number of bits of int.
> When the variable 'currentexp' is left shifted beyond 31 bits then
> the error is produced. Therefore added the conditional expression to 
> verify valid range.
> 
> Tested via syzbot.
> 
> 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>

Please do not have blank lines beween these tags.

You also have trailing whitespace in your changelog text :(

> ---
> v1->v2
> changed the patch
> changed commit message and tested with checkpatch 
> 
> ---
>  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;

Do not make up error codes, please return a valid one and not a random
negative number.  Unless -1 is a valid value for this function?

thanks,

greg k-h

Re: [PATCH v2] UBSAN: shift-out-of-bounds in set_flicker

Posted by Hans Verkuil 2 years, 3 months ago

On 24/08/2023 09:13, Greg KH wrote:
> On Thu, Aug 24, 2023 at 12:36:30PM +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'
>>
>> shift-out-of-bounds error was triggered when variable 
>> 'sd->params.exposure.gain' is greater than the number of bits of int.
>> When the variable 'currentexp' is left shifted beyond 31 bits then
>> the error is produced. Therefore added the conditional expression to 
>> verify valid range.
>>
>> Tested via syzbot.
>>
>> 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>
> 
> Please do not have blank lines beween these tags.
> 
> You also have trailing whitespace in your changelog text :(

And please mention the driver name in your subject! E.g. something like:

"media: gspca/cpia1: UBSAN: shift-out-of-bounds in set_flicker"

That way I can actually know that this is a patch for a driver that I
maintain.

Regards,

	Hans

> 
>> ---
>> v1->v2
>> changed the patch
>> changed commit message and tested with checkpatch 
>>
>> ---
>>  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;
> 
> Do not make up error codes, please return a valid one and not a random
> negative number.  Unless -1 is a valid value for this function?
> 
> thanks,
> 
> greg k-h