linux-kernel - Re: [tip:x86/urgent] x86/fpu/xstate: Fix xcomp

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Message-ID: <20170214225348.GA32055@kroah.com>
Date:   Tue, 14 Feb 2017 14:53:48 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     dave.hansen@...ux.intel.com, linux-kernel@...r.kernel.org,
        ravi.v.shankar@...el.com, torvalds@...ux-foundation.org,
        haokexin@...il.com, tglx@...utronix.de,
        Joakim.Tjernlund@...inera.com, mingo@...nel.org,
        peterz@...radead.org, hpa@...or.com, fenghua.yu@...el.com,
        luto@...nel.org, bp@...e.de, stable@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86/fpu/xstate: Fix xcomp_bv in XSAVES header

On Tue, Feb 14, 2017 at 01:26:41PM -0800, Yu-cheng Yu wrote:
> On Tue, Jan 24, 2017 at 12:46:17AM -0800, tip-bot for Yu-cheng Yu wrote:
> > Commit-ID:  dffba9a31c7769be3231c420d4b364c92ba3f1ac
> > Gitweb:     http://git.kernel.org/tip/dffba9a31c7769be3231c420d4b364c92ba3f1ac
> > Author:     Yu-cheng Yu <yu-cheng.yu@...el.com>
> > AuthorDate: Mon, 23 Jan 2017 14:54:44 -0800
> > Committer:  Ingo Molnar <mingo@...nel.org>
> > CommitDate: Tue, 24 Jan 2017 09:04:48 +0100
> > 
> > x86/fpu/xstate: Fix xcomp_bv in XSAVES header
> > 
> > The compacted-format XSAVES area is determined at boot time and
> > never changed after.  The field xsave.header.xcomp_bv indicates
> > which components are in the fixed XSAVES format.
> > 
> > In fpstate_init() we did not set xcomp_bv to reflect the XSAVES
> > format since at the time there is no valid data.
> > 
> > However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(),
> > as in commit:
> > 
> >   b22cbe404a9c x86/fpu: Fix invalid FPU ptrace state after execve()
> > 
> > and when __fpu_restore_sig() does fpu__restore() for a COMPAT-mode
> > app, a #GP occurs.  This can be easily triggered by doing valgrind on
> > a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and
> > others:
> > 
> > 	https://bugzilla.kernel.org/show_bug.cgi?id=190061
> > 
> > Fix it by setting xcomp_bv correctly.
> > 
> 
> Please consider pulling this into the stable tree because my previous
> patch in commit: 
> 
>   b22cbe404a9c x86/fpu: Fix invalid FPU ptrace state after execve()
> 
> exposes the same issue in the stable tree.

Ah, thanks, I'll do that for the next round of stable releases after the
ones that happen tomorrow.

greg k-h