linux-kernel - Re: [patch V3 66/66] x86/fpu/signal: Let xrstor handle the features to init

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YNL3VXx9QiizOo0T@zn.tnic>
Date:   Wed, 23 Jun 2021 10:56:53 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        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>,
        Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [patch V3 66/66] x86/fpu/signal: Let xrstor handle the features
 to init

On Fri, Jun 18, 2021 at 04:19:29PM +0200, Thomas Gleixner wrote:
> There is no reason to do an extra XRSTOR from initfp_state for feature bits
> which have been cleared by user space in the FX magic xfeatures storage.
> 
> Just clear them in the task's XSTATE header and do a full restore which
> will put these cleared features into init state.
> 
> There is no real difference in performance because the current code already
> does a full restore when the xfeatures bits are preserved as the signal
> frame setup has stored them, which is the full UABI feature set.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/kernel/fpu/signal.c |   92 +++++++++++++++----------------------------
>  1 file changed, 33 insertions(+), 59 deletions(-)

...

> @@ -390,54 +362,56 @@ static int __fpu_restore_sig(void __user
>  		set_thread_flag(TIF_NEED_FPU_LOAD);
>  	}
>  	__fpu_invalidate_fpregs_state(fpu);
> +	__cpu_invalidate_fpregs_state();
>  	fpregs_unlock();
>  
>  	if (use_xsave() && !fx_only) {
> -		u64 init_bv = xfeatures_mask_uabi() & ~user_xfeatures;
> -
> -		ret = copy_sigframe_from_user_to_xstate(&fpu->state.xsave, buf_fx);
> +		ret = copy_sigframe_from_user_to_xstate(&fpu->state.xsave,
> +							buf_fx);

Why? Just let it stick out.

Regardless,

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg