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

From: Andy Lutomirski
Date: Fri Jan 27 2017 - 22:48:38 EST

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.


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.