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Date:   Mon, 18 Oct 2021 10:58:31 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= <toke@toke.dk>
Cc:     Vlad Buslov <vladbu@nvidia.com>, Paolo Abeni <pabeni@redhat.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        syzbot <syzbot+62e474dd92a35e3060d8@syzkaller.appspotmail.com>,
        andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
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        Saeed Mahameed <saeedm@nvidia.com>,
        Maxim Mikityanskiy <maximmi@nvidia.com>
Subject: Re: [syzbot] BUG: corrupted list in netif_napi_add
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On Mon, 18 Oct 2021 19:40:40 +0200 Toke H=C3=B8iland-J=C3=B8rgensen wrote:
> Jakub Kicinski <kuba@kernel.org> writes:
>=20
> > On Mon, 18 Oct 2021 17:04:19 +0300 Vlad Buslov wrote: =20
> >> We got a use-after-free with very similar trace [0] during nightly
> >> regression. The issue happens when ip link up/down state is flipped
> >> several times in loop and doesn't reproduce for me manually. The fact
> >> that it didn't reproduce for me after running test ten times suggests
> >> that it is either very hard to reproduce or that it is a result of some
> >> interaction between several tests in our suite.
> >>=20
> >> [0]:
> >>=20
> >> [ 3187.779569] mlx5_core 0000:08:00.0 enp8s0f0: Link up
> >>  [ 3187.890694] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >>  [ 3187.892518] BUG: KASAN: use-after-free in __list_add_valid+0xc3/0x=
f0
> >>  [ 3187.894132] Read of size 8 at addr ffff8881150b3fb8 by task ip/119=
618 =20
> >
> > Hm, not sure how similar it is. This one looks like channel was freed
> > without deleting NAPI. Do you have list debug enabled? =20
>=20
> Well, the other report[0] also kinda looks like the NAPI thread keeps
> running after it should have been disabled, so maybe they are in fact
> related?
>=20
> [0] https://lore.kernel.org/r/000000000000c1524005cdeacc5f@google.com

Could be, if napi->state gets corrupted it may lose NAPI_STATE_LISTED.

719c57197010 ("net: make napi_disable() symmetric with enable")
3765996e4f0b ("napi: fix race inside napi_enable")
is the only thing that comes to mind, but they look fine to me.