linux-kernel - Re: [GIT PULL] MM updates for 6.1-rc1

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Date:   Tue, 11 Oct 2022 11:59:07 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        mm-commits@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] MM updates for 6.1-rc1

On Tue, Oct 11, 2022 at 11:44:46AM -0700, Josh Poimboeuf wrote:
> On Tue, Oct 11, 2022 at 10:24:27AM +0200, Peter Zijlstra wrote:
> > On Mon, Oct 10, 2022 at 06:20:00PM -0700, Linus Torvalds wrote:
> > > The other thing I notice from just doing a build is that I now get
> > > 
> > >    vmlinux.o: warning: objtool: kasan_report+0x12: call to
> > > stackleak_track_stack() with UACCESS enabled
> > 
> > So kasan_report() is already marked as being special; and it does the
> > mandatory user_access_save() / user_access_restore() things to fix it
> > up.
> > 
> > But it looks like kasan code itself is now getting instrumented by the
> > stackleak stuff and that inserts a call outside of the
> > user_access_save()/restore() thing, and *that* is getting flagged.
> > 
> > Looking at mm/kasan/Makefile it disables a lot of the instrumentation,
> > but perhaps not enough?
> 
> I can recreate, but weirdly the below doesn't seem to fix it.

Duh, because kmsan != stackleak, obviously...

> 
> diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
> index d4837bff3b60..a41cf1235032 100644
> --- a/mm/kasan/Makefile
> +++ b/mm/kasan/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  KASAN_SANITIZE := n
> +KMSAN_SANITIZE := n
>  UBSAN_SANITIZE := n
>  KCOV_INSTRUMENT := n
>  
> 

-- 
Josh