linux-kernel - Re: [PATCH v7 12/18] x86/fsgsbase/64: GSBASE handling with FSGSBASE in the paranoid path

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Message-ID: <alpine.DEB.2.21.1906290936570.1802@nanos.tec.linutronix.de>
Date:   Sat, 29 Jun 2019 09:37:32 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Bae, Chang Seok" <chang.seok.bae@...el.com>
cc:     Andy Lutomirski <luto@...nel.org>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v7 12/18] x86/fsgsbase/64: GSBASE handling with FSGSBASE
 in the paranoid path

On Sat, 29 Jun 2019, Bae, Chang Seok wrote:
> > On May 8, 2019, at 03:02, Chang S. Bae <chang.seok.bae@...el.com> wrote:
> > 
> > ENTRY(paranoid_exit)
> > …
> > +
> > +	/* On FSGSBASE systems, always restore the stashed GSBASE */
> > +	wrgsbase	%rbx
> > +	jmp	.Lparanoid_exit_no_swapgs;
> 
> It would crash any time getting a paranoid entry with user GS but kernel CR3.
> The issue is thankfully uncovered by Vegard N. A relevant test case will be
> published by Andy L. The patch fixes the issue. (Rebased on the tip master.)

Can you please provide a proper patch with a proper changelog?

Thanks,

	tglx