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

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Message-ID: <20221011184444.npthr2pmzqb32x6z@treble>
Date:   Tue, 11 Oct 2022 11:44:44 -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 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.

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