Re: [PATCH v9] fs: clear file privilege bits when mmap writing

[Kees Cook]

On Fri, Jan 27, 2017 at 7:47 PM, Andy Lutomirski <luto@xxxxxxxxxx> wrote:
> On Wed, May 25, 2016 at 2:49 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>> On Wed, May 25, 2016 at 02:36:57PM -0700, Kees Cook wrote:
>>
>>> Hm, this didn't end up getting picked up. (This jumped out at me again
>>> because i_mutex just vanished...)
>>>
>>> Al, what's the right way to update the locking in this patch?
>>
>> ->i_mutex is dealt with just by using lock_inode(inode)/unlock_inode(inode);
>> I hadn't looked at the rest of the locking in there.
>
> Ping?
>
> If this is too messy, I'm wondering if we could get away with a much
> simpler approach: clear the suid and sgid bits when the file is opened
> for write.

I think that'll break something, but I don't have any actual examples.
Regardless, I'd still like to see this hole fixed...

-Kees

-- 
Kees Cook
Pixel Security