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

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Message-ID: <B03AE722-4BAF-4BD1-9A7D-3DD790A7F306@zytor.com>
Date:   Thu, 07 Mar 2019 10:51:59 -0800
From:   hpa@...or.com
To:     Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        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 March 7, 2019 10:48:13 AM PST, Peter Zijlstra <peterz@...radead.org> wrote:
>On Thu, Mar 07, 2019 at 09:54:14AM -0800, Linus Torvalds wrote:
>> On Thu, Mar 7, 2019 at 9:41 AM Peter Zijlstra <peterz@...radead.org>
>wrote:
>> > >
>> > > 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()
>> 
>> Ugh. I think I almost just agree with your decision to just let that
>> memset go unchecked.
>> 
>> I'm not saying it's right, but it doesn't seem to be a fight worth
>fighting.
>
>One think I could do; is add a filter to each function and only allow
>__memset from the kasan code, and not from anywhere else.
>
>Another thing I need to look at is why objtool only found memset_orig
>(from __memset) but not memset_erms, which if I read the code right, is
>a possible alternative there.
>
>> Because AC vs KASAN in general ends up smelling like "not a fight
>> worth fighting" to me. You've done a herculean job, but..
>
>I know,.. I've been so close to doing that so many times, but it
>seems like defeat, esp. since I'm so close now :-)

___memset_kasan()?
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