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Date: Wed, 29 Aug 2018 11:56:08 -0700 From: Nadav Amit <nadav.amit@...il.com> To: Andy Lutomirski <luto@...nel.org>, x86@...nel.org Cc: Borislav Petkov <bp@...en8.de>, Rik van Riel <riel@...riel.com>, 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 at 8:47 AM, Andy Lutomirski <luto@...nel.org> 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> > --- > > Nadav, this is intended for your series. Want to add it right > before the use_temporary_mm() stuff? Sure. Thanks! I will apply the following small fix: > + > +#ifdef CONFIG_DEBUG_VM > + WARN_ON_ONCE(!loaded_mm); > +#endif Will be changed to VM_WARN_ON_ONCE() in the two instances. Regards, Nadav
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