[PATCH v6] fbdev: fbmem: Fix the implicit type casting

[Helge Deller]

On 2/3/22 07:39, Sam Ravnborg wrote:
> Hi Daniel,
>
> I assume you will take this.
>
> Patch is:
> Reviewed-by: Sam Ravnborg <sam at ravnborg.org>


Acked-by: Helge Deller <deller at gmx.de>

Helge

>
> 	Sam
>
> On Wed, Feb 02, 2022 at 03:58:08PM -0800, Yizhuo Zhai wrote:
>> In function do_fb_ioctl(), the "arg" is the type of unsigned long,
>> and in "case FBIOBLANK:" this argument is casted into an int before
>> passig to fb_blank(). In fb_blank(), the comparision
>> if (blank > FB_BLANK_POWERDOWN) would be bypass if the original
>> "arg" is a large number, which is possible because it comes from
>> the user input. Fix this by adding the check before the function
>> call.
>>
>> Signed-off-by: Yizhuo Zhai <yzhai003 at ucr.edu>
>> ---
>>  drivers/video/fbdev/core/fbmem.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
>> index 0fa7ede94fa6..13083ad8d751 100644
>> --- a/drivers/video/fbdev/core/fbmem.c
>> +++ b/drivers/video/fbdev/core/fbmem.c
>> @@ -1160,6 +1160,8 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
>>  		ret = fbcon_set_con2fb_map_ioctl(argp);
>>  		break;
>>  	case FBIOBLANK:
>> +		if (arg > FB_BLANK_POWERDOWN)
>> +			return -EINVAL;
>>  		console_lock();
>>  		lock_fb_info(info);
>>  		ret = fb_blank(info, arg);
>> --
>> 2.25.1