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From:   Eric Dumazet <edumazet@google.com>
Date:   Fri, 30 Jun 2023 13:24:23 +0200
Message-ID: <CANn89i+-JH6xgNW=2+ywp-urUMpOJ-vkCKvUyVFTuyJTTojvUQ@mail.gmail.com>
Subject: Re: [PATCH] net: tls: enable __GFP_ZERO upon tls_init()
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Ard Biesheuvel <ardb@kernel.org>,
        Alexander Potapenko <glider@google.com>,
        Boris Pismenny <borisp@nvidia.com>,
        John Fastabend <john.fastabend@gmail.com>,
        Jakub Kicinski <kuba@kernel.org>, herbert@gondor.apana.org.au,
        linux-crypto@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        syzbot <syzbot+828dfc12440b4f6f305d@syzkaller.appspotmail.com>,
        Eric Biggers <ebiggers@kernel.org>,
        Aviad Yehezkel <aviadye@nvidia.com>,
        Daniel Borkmann <daniel@iogearbox.net>, netdev@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        Paolo Abeni <pabeni@redhat.com>
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On Fri, Jun 30, 2023 at 1:11=E2=80=AFPM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> On 2023/06/30 19:18, Ard Biesheuvel wrote:
> > On Fri, 30 Jun 2023 at 12:11, Alexander Potapenko <glider@google.com> w=
rote:
> >>
> >> On Fri, Jun 30, 2023 at 12:02=E2=80=AFPM Ard Biesheuvel <ardb@kernel.o=
rg> wrote:
> >>>
> >>> On Fri, 30 Jun 2023 at 11:53, Tetsuo Handa
> >>> <penguin-kernel@i-love.sakura.ne.jp> wrote:
> >>>>
> >>>> On 2023/06/30 18:36, Ard Biesheuvel wrote:
> >>>>> Why are you sending this now?
> >>>>
> >>>> Just because this is currently top crasher and I can reproduce local=
ly.
> >>>>
> >>>>> Do you have a reproducer for this issue?
> >>>>
> >>>> Yes. https://syzkaller.appspot.com/text?tag=3DReproC&x=3D12931621900=
000 works.
> >>>>
> >>>
> >>> Could you please share your kernel config and the resulting kernel lo=
g
> >>> when running the reproducer? I'll try to reproduce locally as well,
> >>> and see if I can figure out what is going on in the crypto layer
> >>
> >> The config together with the repro is available at
> >> https://syzkaller.appspot.com/bug?extid=3D828dfc12440b4f6f305d, see th=
e
> >> latest row of the "Crashes" table that contains a C repro.
>
> Kernel is commit e6bc8833d80f of https://github.com/google/kmsan/commits/=
master .
> Config is available in the dashboard page, but a smaller one is available=
 at
> https://I-love.SAKURA.ne.jp/tmp/config-6.4.0-rc7-kmsan .
>
> I'm using a debug printk() patch shown below.
>

Please note that your patch is not correct, unless I am missing something.

sk_page_frag() will use a per-thread frag allocator
(current->task_frag), which might be fed with pages
allocated from other sockets (standard TCP ones), without __GFP_ZERO.

If we must (and I am not saying we should) take this route, we also
need to force
"sk->sk_use_task_frag =3D false" for TLS sockets.