Re: [PATCH v2 1/1] v4l: ioctl: Fix memory leak in video_usercopy

[Bingbu Cao]

On 1/14/21 12:50 PM, Bingbu Cao wrote:
> Sakari,
> 
> On 12/21/20 4:11 AM, Sakari Ailus wrote:
>> When an IOCTL with argument size larger than 128 that also used array
>> arguments were handled, two memory allocations were made but alas, only
>> the latter one of them was released. This happened because there was only
>> a single local variable to hold such a temporary allocation.
>>
>> Fix this by adding separate variables to hold the pointers to the
>> temporary allocations.
>>
>> Reported-by: Arnd Bergmann <arnd@xxxxxxxxxx>
>> Reported-by: syzbot+1115e79c8df6472c612b@xxxxxxxxxxxxxxxxxxxxxxxxx
>> Fixes: d14e6d76ebf7 ("[media] v4l: Add multi-planar ioctl handling code")
>> Cc: stable@xxxxxxxxxxxxxxx
>> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
>> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
>> ---
>>  drivers/media/v4l2-core/v4l2-ioctl.c | 32 ++++++++++++----------------
>>  1 file changed, 14 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>> index 3198abdd538c..9906b41004e9 100644
>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>> @@ -3283,7 +3283,7 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
>>  	       v4l2_kioctl func)
>>  {
>>  	char	sbuf[128];
>> -	void    *mbuf = NULL;
>> +	void    *mbuf = NULL, *array_buf = NULL;
>>  	void	*parg = (void *)arg;
>>  	long	err  = -EINVAL;
>>  	bool	has_array_args;
>> @@ -3318,27 +3318,21 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
>>  	has_array_args = err;
>>  
>>  	if (has_array_args) {
>> -		/*
>> -		 * When adding new types of array args, make sure that the
>> -		 * parent argument to ioctl (which contains the pointer to the
>> -		 * array) fits into sbuf (so that mbuf will still remain
>> -		 * unused up to here).
>> -		 */
>> -		mbuf = kvmalloc(array_size, GFP_KERNEL);
>> +		array_buf = kvmalloc(array_size, GFP_KERNEL);
>>  		err = -ENOMEM;
>> -		if (NULL == mbuf)
>> +		if (array_buf == NULL)
> 
> if (!array_buf)
> ?
> 
Please ignore my previous comment, as the patch was landed. :)
....
-- 
Best regards,
Bingbu Cao