linux-kernel - Re: [PATCH v2 12/18] x86/espfix/64: Stop assuming that pt

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Message-ID: <alpine.DEB.2.20.1711232036090.2364@nanos>
Date:   Thu, 23 Nov 2017 20:36:22 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
cc:     X86 ML <x86@...nel.org>, Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v2 12/18] x86/espfix/64: Stop assuming that pt_regs is
 on the entry stack

On Tue, 21 Nov 2017, Andy Lutomirski wrote:

> When we start using an entry trampoline, a #GP from userspace will
> be delivered on the entry stack, not on the task stack.  Fix the
> espfix64 #DF fixup to set up #GP according to TSS.SP0, rather than
> assuming that pt_regs + 1 == SP0.  This won't change anything
> without an entry stack, but it will make the code continue to work
> when an entry stack is added.
> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>