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Message-ID: <87mtrjfrnc.ffs@nanos.tec.linutronix.de>
Date: Mon, 21 Jun 2021 12:17:43 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: 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>
Subject: Re: [patch V3 15/66] x86/fpu: Fail ptrace() requests that try to set invalid MXCSR values
On Fri, Jun 18 2021 at 16:18, Thomas Gleixner wrote:
> From: Andy Lutomirski <luto@...nel.org>
>
> There is no benefit from accepting and silently changing an invalid MXCSR
> value supplied via ptrace(). Instead, return -EINVAL on invalid input.
>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> V2: New patch. Picked up from Andy.
> ---
> arch/x86/kernel/fpu/regset.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
> ---
> --- a/arch/x86/kernel/fpu/regset.c
> +++ b/arch/x86/kernel/fpu/regset.c
> @@ -64,8 +64,9 @@ int xfpregs_set(struct task_struct *targ
> if (ret)
> return ret;
>
> - /* Mask invalid MXCSR bits (for historical reasons). */
> - newstate.mxcsr &= mxcsr_feature_mask;
> + /* Do not allow an invalid MXCSR value. */
> + if (newstate.mxcsr & ~mxcsr_feature_mask)
> + ret = -EINVAL;
This obviously needs to be:
return -EINVAL;
/me goes to find a brown paperbag
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