linux-kernel - Re: [PATCH] ptrace: restore smp_rmb() in __ptrace_may

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Message-ID: <87ef4gzpjw.fsf@xmission.com>
Date:   Wed, 29 May 2019 20:41:55 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Jann Horn <jannh@...gle.com>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        David Howells <dhowells@...hat.com>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ptrace: restore smp_rmb() in __ptrace_may_access()

Jann Horn <jannh@...gle.com> writes:

> I'm actually trying to get rid of the ->mm access in
> __ptrace_may_access() entirely by moving the dumpability and the
> user_ns into the signal_struct, but I don't have patches for that
> ready (yet).

Do you have a plan for dealing with old linux-threads style threads
where you have two processes that share the same mm, but have different
signal_structs.

I don't think it is required to share any other structures except
mm_struct when you share mm_struct.  Maybe sighand_struct.

Not to derail your idea.  Only needing to look at signal_struct sounds
very nice.  I just know we have some other somewhat bizarre cases the
kernel still supports.

Eric