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Date:   Wed, 27 Feb 2019 18:30:46 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>, Peter Anvin <hpa@zytor.com>,
        Julien Thierry <julien.thierry@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Ingo Molnar <mingo@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        James Morse <james.morse@arm.com>, valentin.schneider@arm.com,
        Brian Gerst <brgerst@gmail.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH 5/6] objtool: Add UACCESS validation
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On Wed, Feb 27, 2019 at 08:18:21AM -0800, Linus Torvalds wrote:

> So the whole "run with AC on" thing isn't a big deal, apart from the
> scheduling case.
> 
> And we know how to fix the scheduling case by just doing the
> save/restore thing..

Right, but I was hoping to avoid having to do that; and I think we can
do that if we push all of kasan_report into an exception, like that
'patch' I just posted.

If I'm not mistaken the regular kasan house-keeping crud just prods at
the shadow memory with simple code and should be perfectly safe.