Re: [PATCH 1/5] seccomp: don't use semaphore and wait_queue together

[Andrei Vagin]

On Wed, Oct 19, 2022 at 10:10:44PM -0700, Kees Cook wrote:
> On October 19, 2022 6:10:44 PM PDT, Andrei Vagin <avagin@xxxxxxxxx> wrote:
> >Here is no reason to use two different primitives that do similar things.
> >
> >Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx>
> >---
> > kernel/seccomp.c | 41 ++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 36 insertions(+), 5 deletions(-)
> 
> The commit log does not justify adding 29 lines to "do similar
> things". :) Can you describe the rationale and benefits here a bit
> more? I assume this to use the the future new wake_up helper?

The main reason is to use new wake_up helpers, but there are a few
other reasons:

* if we use two different ways, we always need to call them both. This
  patch fixes seccomp_notify_recv where we forgot to call wake_up_poll
  in the error path.

* If we use one primitive, we can control how many waiters are woken up
  for each request. Our goal is to wake up just one that will handle a
  request. Right now, wake_up_poll may wake up one waiter and
  up(&match->notif->request) may wake up one more.

I will update the commit message. Thanks!

> 
> 
> -- 
> Kees Cook