Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220225123953.3251327-1-alexandre.ghiti@canonical.com> <CANpmjNN304EZfFN2zobxKGXbXWXAfr92nP1KvtR7j-YqSFShvQ@mail.gmail.com>
In-Reply-To: <CANpmjNN304EZfFN2zobxKGXbXWXAfr92nP1KvtR7j-YqSFShvQ@mail.gmail.com>
From:   Alexandre Ghiti <alexandre.ghiti@canonical.com>
Date:   Fri, 25 Feb 2022 15:04:18 +0100
Message-ID: <CA+zEjCtuwnKdi8EuyGWaYNFa7KsYcH9B1mYke6YALo+C1Nq+Dw@mail.gmail.com>
Subject: Re: [PATCH -fixes v3 0/6] Fixes KASAN and other along the way
To:     Marco Elver <elver@google.com>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Aleksandr Nogikh <nogikh@google.com>,
        Nick Hu <nickhu@andestech.com>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        kasan-dev@googlegroups.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Feb 25, 2022 at 2:06 PM Marco Elver <elver@google.com> wrote:
>
> On Fri, 25 Feb 2022 at 13:40, Alexandre Ghiti
> <alexandre.ghiti@canonical.com> wrote:
> >
> > As reported by Aleksandr, syzbot riscv is broken since commit
> > 54c5639d8f50 ("riscv: Fix asan-stack clang build"). This commit actually
> > breaks KASAN_INLINE which is not fixed in this series, that will come later
> > when found.
> >
> > Nevertheless, this series fixes small things that made the syzbot
> > configuration + KASAN_OUTLINE fail to boot.
> >
> > Note that even though the config at [1] boots fine with this series, I
> > was not able to boot the small config at [2] which fails because
> > kasan_poison receives a really weird address 0x4075706301000000 (maybe a
> > kasan person could provide some hint about what happens below in
> > do_ctors -> __asan_register_globals):
>
> asan_register_globals is responsible for poisoning redzones around
> globals. As hinted by 'do_ctors', it calls constructors, and in this
> case a compiler-generated constructor that calls
> __asan_register_globals with metadata generated by the compiler. That
> metadata contains information about global variables. Note, these
> constructors are called on initial boot, but also every time a kernel
> module (that has globals) is loaded.
>
> It may also be a toolchain issue, but it's hard to say. If you're
> using GCC to test, try Clang (11 or later), and vice-versa.

I tried 3 different gcc toolchains already, but that did not fix the
issue. The only thing that worked was setting asan-globals=0 in
scripts/Makefile.kasan, but ok, that's not a fix.
I tried to bisect this issue but our kasan implementation has been
broken quite a few times, so it failed.

I keep digging!

Thanks for the tips,

Alex