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

[Rik van Riel]

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@xxxxxxxxxxxxxxx
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxxx>

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