linux-kernel - Re: [PATCH 2/9] signal/seccomp: Refactor seccomp signal and coredump generation

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Message-ID: <202106252014.5AE600929@keescook>
Date:   Fri, 25 Jun 2021 20:17:51 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Michael Schmitz <schmitzmic@...il.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>, Oleg Nesterov <oleg@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        alpha <linux-alpha@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Arnd Bergmann <arnd@...nel.org>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 2/9] signal/seccomp: Refactor seccomp signal and coredump
 generation

On Thu, Jun 24, 2021 at 01:59:55PM -0500, Eric W. Biederman wrote:
> 
> Factor out force_sig_seccomp from the seccomp signal generation and
> place it in kernel/signal.c.  The function force_sig_seccomp takes a
> paramter force_coredump to indicate that the sigaction field should be
> reset to SIGDFL so that a coredump will be generated when the signal
> is delivered.

Ah! This is the part I missed when I was originally trying to figure
out the coredump stuff. It's the need for setting a default handler
(i.e. doing a coredump)?

> force_sig_seccomp is then used to replace both seccomp_send_sigsys
> and seccomp_init_siginfo.
> 
> force_sig_info_to_task gains an extra parameter to force using
> the default signal action.
> 
> With this change seccomp is no longer a special case and there
> becomes exactly one place do_coredump is called from.

Looks good to me. This may benefit from force_sig_seccomp() to be wrapped
in an #ifdef CONFIG_SECCOMP.

(This patch reminds me that the seccomp self tests don't check for core
dumps...)

-- 
Kees Cook