linux-kernel - Re: [PATCH v2] x86/nmi: Fix some races in NMI uaccess

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Message-ID: <9ff9dd41ff99560dcb3eb78f5835da67293f860c.camel@surriel.com>
Date:   Wed, 29 Aug 2018 12:06:54 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
        Nadav Amit <nadav.amit@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>, Jann Horn <jannh@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2] x86/nmi: Fix some races in NMI uaccess

On Wed, 2018-08-29 at 08:47 -0700, Andy Lutomirski wrote:
> In NMI context, we might be in the middle of context switching or in
> the middle of switch_mm_irqs_off().  In either case, CR3 might not
> match current->mm, which could cause copy_from_user_nmi() and
> friends to read the wrong memory.
> 
> Fix it by adding a new nmi_uaccess_okay() helper and checking it in
> copy_from_user_nmi() and in __copy_from_user_nmi()'s callers.
> 
> Cc: stable@...r.kernel.org
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Nadav Amit <nadav.amit@...il.com>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>

Reviewed-by: Rik van Riel <riel@...riel.com>

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