Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 7 Mar 2019 19:48:13 +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>,
        Dmitry Vyukov <dvyukov@google.com>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 18/20] objtool: Add UACCESS validation
Message-ID: <20190307184813.GL32477@hirez.programming.kicks-ass.net>
References: <20190307114511.870090179@infradead.org>
 <20190307115200.697533978@infradead.org>
 <CAHk-=wgKDSSoV5WvO018hoPPSHO=TQ3wwnfOtCpaENceBe0Z6Q@mail.gmail.com>
 <20190307174135.GJ32477@hirez.programming.kicks-ass.net>
 <CAHk-=wgGZWXQj-J2xo0DY7150VrXOSqoD5Dj1_LGYaotqA6Z-Q@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAHk-=wgGZWXQj-J2xo0DY7150VrXOSqoD5Dj1_LGYaotqA6Z-Q@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@infradead.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 :-)