linux-kernel - Re: [PATCH 11/20] signal/s390: Use force_sigsegv in default_trap

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Message-ID: <202110210917.FEED0F8@keescook>
Date:   Thu, 21 Oct 2021 09:17:41 -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>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH 11/20] signal/s390: Use force_sigsegv in
 default_trap_handler

On Wed, Oct 20, 2021 at 12:43:57PM -0500, Eric W. Biederman wrote:
> Reading the history it is unclear why default_trap_handler calls
> do_exit.  It is not even menthioned in the commit where the change
> happened.  My best guess is that because it is unknown why the
> exception happened it was desired to guarantee the process never
> returned to userspace.
> 
> Using do_exit(SIGSEGV) has the problem that it will only terminate one
> thread of a process, leaving the process in an undefined state.
> 
> Use force_sigsegv(SIGSEGV) instead which effectively has the same
> behavior except that is uses the ordinary signal mechanism and
> terminates all threads of a process and is generally well defined.
> 
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> Cc: linux-s390@...r.kernel.org
> Fixes: ca2ab03237ec ("[PATCH] s390: core changes")
> History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

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

-- 
Kees Cook