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

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Message-ID: <202110210923.F5BE43C@keescook>
Date:   Thu, 21 Oct 2021 09:24:22 -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 Wed, Oct 20, 2021 at 12:43:59PM -0500, Eric W. Biederman wrote:
> Add a simple helper force_fatal_sig that causes a signal to be
> delivered to a process as if the signal handler was set to SIG_DFL.
> 
> Reimplement force_sigsegv based upon this new helper.  This fixes
> force_sigsegv so that when it forces the default signal handler
> to be used the code now forces the signal to be unblocked as well.
> 
> Reusing the tested logic in force_sig_info_to_task that was built for
> force_sig_seccomp this makes the implementation trivial.
> 
> 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?

> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook