netdev - Re: [PATCH] net: tls: enable __GFP_ZERO upon tls

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Date: Fri, 30 Jun 2023 13:24:23 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc: Ard Biesheuvel <ardb@...nel.org>, Alexander Potapenko <glider@...gle.com>, 
	Boris Pismenny <borisp@...dia.com>, John Fastabend <john.fastabend@...il.com>, 
	Jakub Kicinski <kuba@...nel.org>, herbert@...dor.apana.org.au, linux-crypto@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com, 
	syzbot <syzbot+828dfc12440b4f6f305d@...kaller.appspotmail.com>, 
	Eric Biggers <ebiggers@...nel.org>, Aviad Yehezkel <aviadye@...dia.com>, 
	Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org, 
	"David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH] net: tls: enable __GFP_ZERO upon tls_init()

On Fri, Jun 30, 2023 at 1:11 PM Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
>
> On 2023/06/30 19:18, Ard Biesheuvel wrote:
> > On Fri, 30 Jun 2023 at 12:11, Alexander Potapenko <glider@...gle.com> wrote:
> >>
> >> On Fri, Jun 30, 2023 at 12:02 PM Ard Biesheuvel <ardb@...nel.org> wrote:
> >>>
> >>> On Fri, 30 Jun 2023 at 11:53, Tetsuo Handa
> >>> <penguin-kernel@...ove.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 locally.
> >>>>
> >>>>> Do you have a reproducer for this issue?
> >>>>
> >>>> Yes. https://syzkaller.appspot.com/text?tag=ReproC&x=12931621900000 works.
> >>>>
> >>>
> >>> Could you please share your kernel config and the resulting kernel log
> >>> 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=828dfc12440b4f6f305d, see the
> >> 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 = false" for TLS sockets.