Re: [PATCH] media: v4l2-compat-ioctl32: don't oops on overlay

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On 29/03/18 15:00, Mauro Carvalho Chehab wrote:
> Em Thu, 29 Mar 2018 10:40:23 +0200
> Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
> 
>> Hi Mauro,
>>
>> On 28/03/18 19:59, Mauro Carvalho Chehab wrote:
>>> At put_v4l2_window32(), it tries to access kp->clips. However,
>>> kp points to an userspace pointer. So, it should be obtained
>>> via get_user(), otherwise it can OOPS:
>>>   
>>
>> <snip>
>>
>>>
>>> cc: stable@xxxxxxxxxxxxxxx
>>> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
>>> ---
>>>  drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
>>> index 5198c9eeb348..4312935f1dfc 100644
>>> --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
>>> +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
>>> @@ -101,7 +101,7 @@ static int get_v4l2_window32(struct v4l2_window __user *kp,
>>>  static int put_v4l2_window32(struct v4l2_window __user *kp,
>>>  			     struct v4l2_window32 __user *up)
>>>  {
>>> -	struct v4l2_clip __user *kclips = kp->clips;
>>> +	struct v4l2_clip __user *kclips;
>>>  	struct v4l2_clip32 __user *uclips;
>>>  	compat_caddr_t p;
>>>  	u32 clipcount;
>>> @@ -116,6 +116,8 @@ static int put_v4l2_window32(struct v4l2_window __user *kp,
>>>  	if (!clipcount)
>>>  		return 0;
>>>  
>>> +	if (get_user(kclips, &kp->clips))
>>> +		return -EFAULT;
>>>  	if (get_user(p, &up->clips))
>>>  		return -EFAULT;
>>>  	uclips = compat_ptr(p);
>>>   
>>
>> Reviewed-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>>
>> I have no idea why I didn't find this when I tested this with v4l2-compliance,
>> but the code was certainly wrong.
> 
> I built 4.16-rc4 with KASAN enabled. Perhaps, it won't OOPS without
> it. Yet, I doubt it would work without this fix.

I definitely did not have KASAN enabled when I tested this.

Regards,

	Hans

> 
>>
>> Thank you for debugging this!
> 
> Anytime.
> 
> Thanks,
> Mauro
> 




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