linux-kernel - Re: [patch V3 61/66] x86/fpu/signal: Sanitize the xstate check on sigframe

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Date:   Fri, 18 Jun 2021 22:02:57 +0100
From:   Andrew Cooper <andrew.cooper3@...rix.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
CC:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        "Sebastian Andrzej Siewior" <bigeasy@...utronix.de>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>
Subject: Re: [patch V3 61/66] x86/fpu/signal: Sanitize the xstate check on
 sigframe

On 18/06/2021 15:19, Thomas Gleixner wrote:
> Utilize the check for the extended state magic in the FX software reserved
> bytes and set the parameters for restoring fx_only in the relevant members
> of fw_sw_user.
>
> This allows further cleanups on top because the data is consistent.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/kernel/fpu/signal.c |   69 +++++++++++++++++++------------------------
>  1 file changed, 32 insertions(+), 37 deletions(-)
>
> --- a/arch/x86/kernel/fpu/signal.c
> +++ b/arch/x86/kernel/fpu/signal.c
> @@ -15,29 +15,29 @@
>  #include <asm/sigframe.h>
>  #include <asm/trace/fpu.h>
>  
> -static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
> +static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32 __ro_after_init;

You probably want a second __ro_after_init here.

~Andrew