linux-kernel - Re: [5.2 regression] copy_fpstate_to_sigframe() change causing crash in 32-bit process

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Message-ID: <20190605140405.2nnpqslnjpfe2ig2@linutronix.de>
Date:   Wed, 5 Jun 2019 16:04:05 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Borislav Petkov <bp@...e.de>, Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        kvm ML <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Rik van Riel <riel@...riel.com>, x86-ml <x86@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [5.2 regression] copy_fpstate_to_sigframe() change causing crash
 in 32-bit process

On 2019-06-04 11:53:58 [-0700], Eric Biggers wrote:
> On latest Linus' tree I'm getting a crash in a 32-bit Wine process.
> 
> I bisected it to the following commit:
> 
> commit 39388e80f9b0c3788bfb6efe3054bdce0c3ead45
> Author: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Date:   Wed Apr 3 18:41:35 2019 +0200
> 
>     x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()
> 
> Reverting the commit by applying the following diff makes the problem go away.

This looked like a merge artifact and it has been confirmed as such. Now
you say that this was a needed piece of code. Interesting.
Is that wine process/testcase something you can share? I will try to
take a closer look.

Sebastian