linux-kernel - Re: [PATCH 13/20] signal: Implement force_fatal

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Message-ID: <202110210938.FCB7CEB96F@keescook>
Date:   Thu, 21 Oct 2021 09:39:44 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 13/20] signal: Implement force_fatal_sig

On Thu, Oct 21, 2021 at 11:33:43AM -0500, Eric W. Biederman wrote:
> Kees Cook <keescook@...omium.org> writes:
> 
> > On Wed, Oct 20, 2021 at 12:43:59PM -0500, Eric W. Biederman wrote:
> >> This is interesting both because it makes force_sigsegv simpler and
> >> because there are a couple of buggy places in the kernel that call
> >> do_exit(SIGILL) or do_exit(SIGSYS) because there is no straight
> >> forward way today for those places to simply force the exit of a
> >> process with the chosen signal.  Creating force_fatal_sig allows
> >> those places to be implemented with normal signal exits.
> >
> > I assume this is talking about seccomp()? :) Should a patch be included
> > in this series to change those?
> 
> Actually it is not talking about seccomp.  As far as I can tell seccomp
> is deliberately only killing a single thread when it calls do_exit.

Okay, I wasn't entirely sure, but yes, seccomp wants to keep the "kill
only 1 thread" option, which is weird, but useful for the threaded
seccomp monitor case.

> I am thinking about places where we really want the entire process to
> die and not just a single thread.  Please see the following changes
> where I actually use force_fatal_sig.

Yeah, I saw that now. Thanks!

-- 
Kees Cook