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Date:   Wed, 27 Jan 2021 15:30:25 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com,
        tglx@linutronix.de, mingo@redhat.com
Subject: Re: [PATCH] x86/msr: Filter msr write by X86_IOC_WRMSR_REGS ioctl
Message-ID: <20210127143025.GD17424@zn.tnic>
References: <20210127122456.13939-1-misono.tomohiro@jp.fujitsu.com>
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On Wed, Jan 27, 2021 at 09:24:56PM +0900, Misono Tomohiro wrote:
> commit a7e1f67ed29f ("x86/msr: Filter MSR writes") introduces a
> module parameter to disable writing to msr device file (and add_taint()
> upon writing). As msr register can be written by X86_IOC_WRMSR_REGS
> ioctl too, they should be applied to the ioctl as well.

Blergh, I missed that. :-\

> Fixes: a7e1f67ed29f ("x86/msr: Filter MSR writes")
> Signed-off-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
> ---
> Hello,
> 
> I just noticed this when I read the code.
> I'm not sure if anyone uses ioctl interface now, but I tested this
> by resetting IA32_MPERF by X86_IOC_WRMSR_REGS ioctl.

Yeah, I'm sure once this hits people's kernels, someone will complain.

In any case, good catch, thanks!

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette