linux-kernel - Re: [PATCH] x86/ptrace: Remove questionable TS

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Message-ID: <20160620153110.GB28057@redhat.com>
Date:	Mon, 20 Jun 2016 17:31:11 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/ptrace: Remove questionable TS_COMPAT usage in
	ptrace

On 06/19, Andy Lutomirski wrote:
>
> On Sun, Jun 19, 2016 at 2:19 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > And this leads to another question, why do we actually need to set/clear
> > TS_COMPAT in set_personality_ia32() ??
>
> Something's clearly buggy there, considering that
> set_personality_64bit() does *not* clear it.

Yes, yes, I too noticed this, and this doesn't match the "if (x32)"
branch in set_personality_ia32().

But I think we do not really need to clear this bit. And probably
set_personality_ia32() doesn't need to play with TS_COMPAT.

Oleg.