Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect

[Yu Zhao]

On Mon, Dec 21, 2020 at 12:26:22PM -0800, Linus Torvalds wrote:
> On Mon, Dec 21, 2020 at 12:23 PM Nadav Amit <nadav.amit@xxxxxxxxx> wrote:
> >
> > Using mmap_write_lock() was my initial fix and there was a strong pushback
> > on this approach due to its potential impact on performance.
> 
> From whom?
> 
> Somebody who doesn't understand that correctness is more important
> than performance? And that userfaultfd is not the most important part
> of the system?
> 
> The fact is, userfaultfd is CLEARLY BUGGY.
> 
>           Linus

Fair enough.

Nadav, for your patch (you might want to update the commit message).

Reviewed-by: Yu Zhao <yuzhao@xxxxxxxxxx>

While we are all here, there is also clear_soft_dirty() that could
use a similar fix...