Re: [PATCH] videobuf2-core: take mmap_sem before calling __qbuf_userptr

[Hans Verkuil <hverkuil@xs4all.nl>]

On 08/22/2014 07:34 PM, Jan Kara wrote:
> On Fri 22-08-14 18:01:09, Hans Verkuil wrote:
>> Commit f035eb4e976ef5a059e30bc91cfd310ff030a7d3 (videobuf2: fix lockdep warning)
>> unfortunately removed the mmap_sem lock that is needed around the call to
>> __qbuf_userptr. Amazingly nobody noticed this until Jan Kara pointed this out
>> to me.
>>
>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>> Reported-by: Jan Kara <jack@suse.cz>
> ...
>> @@ -1627,7 +1628,9 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
>>  		ret = __qbuf_mmap(vb, b);
>>  		break;
>>  	case V4L2_MEMORY_USERPTR:
>   I guess you are missing something like:
> 
> mmap_sem = &current->mm->mmap_sem;

Insert <red face>.

Oops, I'll repost.

Regards,

	Hans

> 
> 								Honza
>> +		down_read(mmap_sem);
>>  		ret = __qbuf_userptr(vb, b);
>> +		up_read(mmap_sem);
>>  		break;
>>  	case V4L2_MEMORY_DMABUF:
>>  		ret = __qbuf_dmabuf(vb, b);
>> -- 
>> 2.0.1
>>