linux-kernel - Re: [PATCH 1/3] x86/microcode/intel: Refactor Intel microcode blob loading

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Date:   Fri, 5 Apr 2019 23:59:54 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>
cc:     LKML <linux-kernel@...r.kernel.org>, Jann Horn <jannh@...gle.com>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 1/3] x86/microcode/intel: Refactor Intel microcode blob
 loading

On Fri, 5 Apr 2019, Borislav Petkov wrote:

> From: Jann Horn <jannh@...gle.com>
> 
> Change generic_load_microcode() to use the iov_iter API instead of a
> clumsy open-coded version which has to pay attention to __user data
> or kernel data, depending on the loading method. This allows to avoid
> explicit casting between user and kernel pointers.
> 
> Because the iov_iter API makes it hard to read the same location twice,
> as a side effect, also fix a double-read of the microcode header (which
> could e.g. lead to out-of-bounds reads in microcode_sanity_check()).
> 
> Not that it matters much, only root is allowed to load microcode
> anyway...

Nice!

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>