linux-kernel - Re: [PATCH] x86/msr: Filter msr write by X86_IOC_WRMSR

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Date:   Wed, 27 Jan 2021 15:30:25 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Misono Tomohiro <misono.tomohiro@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
        tglx@...utronix.de, mingo@...hat.com
Subject: Re: [PATCH] x86/msr: Filter msr write by X86_IOC_WRMSR_REGS ioctl

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@...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