linux-kernel - Re: [PATCH 18/20] objtool: Add UACCESS validation

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Date:   Thu, 7 Mar 2019 18:41:35 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, Peter Anvin <hpa@...or.com>,
        Julien Thierry <julien.thierry@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>, valentin.schneider@....com,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 18/20] objtool: Add UACCESS validation

On Thu, Mar 07, 2019 at 08:33:26AM -0800, Linus Torvalds wrote:
> On Thu, Mar 7, 2019 at 3:52 AM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > XXX: are we sure we want __memset marked AC-safe?
> 
> It's certainly one of the safer functions to call with AC set, but it
> sounds wrong anyway. It's not like it's likely to leak kernel data
> (most memset's are with 0, and even the non-zero ones I can't imagine
> are sensitive - more like poison values etc).
> 
> What's the call site that made you go "just add __memset() to the list"?

__asan_{,un}poinson_stack_memory()
  kasan_{,un}poison_shadow()
    __memset()