Re: [patch v2] fcntl: return -EFAULT if copy_to_user fails

[Dan Carpenter <error27@gmail.com>]

On Thu, Jun 03, 2010 at 09:16:52PM +0900, Takuya Yoshikawa wrote:
> (2010/06/03 20:59), Jens Axboe wrote:
>> On 2010-06-03 12:35, Dan Carpenter wrote:
>>> copy_to_user() returns the number of bytes remaining, but we want to
>>> return -EFAULT.
>>> 	ret = fcntl(fd, F_SETOWN_EX, NULL);
>>> With the original code ret would be 8 here.
>>>
>>> V2: Takuya Yoshikawa pointed out a similar issue in f_getown_ex()
>>
>> Pretty basic bug, how long has this been there?
>
> IIUC, from the beginning, when these were introduced.
>
> And I recently sent similar bug fixes for other parts.
>

It was your clear_user() patch which inspired me.  I wrote a smatch
check to find these.  I've pushed the code to the smatch repo.
http://repo.or.cz/r/smatch.git

The heuristic I use is that if we return a variable which is the 
return value of copy_to_user() and it's non-zero then complain.  It 
didn't find the f_getown_ex() because that return value could come from
copy_to_user() or it could be -EINVAL.

I'll mess with it a bit and see if I can make it catch the f_getown_ex()
bug.

regards,
dan carpenter