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From:   Alexander Potapenko <glider@google.com>
Date:   Mon, 9 Oct 2023 14:15:25 +0200
Message-ID: <CAG_fn=W0OO4GGS0-pnHFpnWGsBN3dZJ9tnRxPmEKRkkP4Vh48A@mail.gmail.com>
Subject: Re: [PATCH v2 12/19] lib/stackdepot: use list_head for stack record links
To:     Andrew Morton <akpm@linux-foundation.org>,
        andrey.konovalov@linux.dev
Cc:     Anders Roxell <anders.roxell@linaro.org>,
        Marco Elver <elver@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Vlastimil Babka <vbabka@suse.cz>, kasan-dev@googlegroups.com,
        Evgenii Stepanov <eugenis@google.com>,
        Oscar Salvador <osalvador@suse.de>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>, arnd@arndb.de,
        sfr@canb.auug.org.au
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On Sat, Sep 16, 2023 at 10:04=E2=80=AFPM Andrew Morton
<akpm@linux-foundation.org> wrote:
>
> On Sat, 16 Sep 2023 19:43:35 +0200 Anders Roxell <anders.roxell@linaro.or=
g> wrote:
>
> > On 2023-09-13 19:14, andrey.konovalov@linux.dev wrote:
> > > From: Andrey Konovalov <andreyknvl@google.com>
> > >
> > > Switch stack_record to use list_head for links in the hash table
> > > and in the freelist.
> > >
> > > This will allow removing entries from the hash table buckets.
> > >
> > > This is preparatory patch for implementing the eviction of stack reco=
rds
> > > from the stack depot.
> > >
> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > >
> >
> > Building on an arm64 kernel from linux-next tag next-20230915, and boot
> > that in QEMU. I see the following kernel panic.
> >
> > ...
> >
> > The full log can be found [1] and the .config file [2]. I bisected down
> > to this commit, see the bisect log [3].

I am also seeing similar crashes on an x86 KMSAN build.

They are happening when in the following code:

        list_for_each(pos, bucket) {
                found =3D list_entry(pos, struct stack_record, list);
                if (found->hash =3D=3D hash &&
                    found->size =3D=3D size &&
                    !stackdepot_memcmp(entries, found->entries, size))
                        return found;
        }

`found` is NULL

@Andrey, could you please take a look?