From: John Fastabend <john.fastabend@gmail.com>
To: Jakub Sitnicki <jakub@cloudflare.com>,
John Fastabend <john.fastabend@gmail.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
daniel@iogearbox.net, ast@kernel.org, song@kernel.org,
jonathan.lemon@gmail.com
Subject: Re: [bpf PATCH v2 1/8] bpf: sockmap/tls, during free we may call tcp_bpf_unhash() in loop
Date: Mon, 13 Jan 2020 19:19:52 -0800 [thread overview]
Message-ID: <5e1d3358ae3f0_78752af1940225b430@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <87pnfnscvl.fsf@cloudflare.com>
Jakub Sitnicki wrote:
> On Sat, Jan 11, 2020 at 07:11 AM CET, John Fastabend wrote:
> > When a sockmap is free'd and a socket in the map is enabled with tls
> > we tear down the bpf context on the socket, the psock struct and state,
> > and then call tcp_update_ulp(). The tcp_update_ulp() call is to inform
> > the tls stack it needs to update its saved sock ops so that when the tls
> > socket is later destroyed it doesn't try to call the now destroyed psock
> > hooks.
> >
> > This is about keeping stacked ULPs in good shape so they always have
> > the right set of stacked ops.
> >
> > However, recently unhash() hook was removed from TLS side. But, the
> > sockmap/bpf side is not doing any extra work to update the unhash op
> > when is torn down instead expecting TLS side to manage it. So both
> > TLS and sockmap believe the other side is managing the op and instead
> > no one updates the hook so it continues to point at tcp_bpf_unhash().
> > When unhash hook is called we call tcp_bpf_unhash() which detects the
> > psock has already been destroyed and calls sk->sk_prot_unhash() which
> > calls tcp_bpf_unhash() yet again and so on looping and hanging the core.
> >
> > To fix have sockmap tear down logic fixup the stale pointer.
> >
> > Fixes: 5d92e631b8be ("net/tls: partially revert fix transition through disconnect with close")
> > Reported-by: syzbot+83979935eb6304f8cd46@syzkaller.appspotmail.com
> > Cc: stable@vger.kernel.org
> > Acked-by: Song Liu <songliubraving@fb.com>
> > Signed-off-by: John Fastabend <john.fastabend@gmail.com>
> > ---
> > include/linux/skmsg.h | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
> > index ef7031f8a304..b6afe01f8592 100644
> > --- a/include/linux/skmsg.h
> > +++ b/include/linux/skmsg.h
> > @@ -358,6 +358,7 @@ static inline void sk_psock_update_proto(struct sock *sk,
> > static inline void sk_psock_restore_proto(struct sock *sk,
> > struct sk_psock *psock)
> > {
> > + sk->sk_prot->unhash = psock->saved_unhash;
>
> We could also restore it from psock->sk_proto->unhash if we were not
> NULL'ing on first call, right?
>
> I've been wondering what is the purpose of having psock->saved_unhash
> and psock->saved_close if we have the whole sk->sk_prot saved in
> psock->sk_proto.
Its historical we can do some cleanups in net-next to simplify this a bit.
I don't think it needs to be done in bpf tree though.
>
> > sk->sk_write_space = psock->saved_write_space;
> >
> > if (psock->sk_proto) {
>
> Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
next prev parent reply other threads:[~2020-01-14 3:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-11 6:11 [bpf PATCH v2 0/8] Fixes for sockmap/tls from more complex BPF progs John Fastabend
2020-01-11 6:11 ` [bpf PATCH v2 1/8] bpf: sockmap/tls, during free we may call tcp_bpf_unhash() in loop John Fastabend
2020-01-13 13:29 ` Jakub Sitnicki
2020-01-14 3:19 ` John Fastabend [this message]
2020-01-11 6:12 ` [bpf PATCH v2 2/8] bpf: sockmap, ensure sock lock held during tear down John Fastabend
2020-02-05 17:55 ` Jakub Sitnicki
2020-02-06 5:51 ` John Fastabend
2020-02-06 12:26 ` Jakub Sitnicki
2020-02-06 19:04 ` John Fastabend
2020-01-11 6:12 ` [bpf PATCH v2 3/8] bpf: sockmap/tls, push write_space updates through ulp updates John Fastabend
2020-01-12 1:00 ` Jonathan Lemon
2020-01-13 13:59 ` Jakub Sitnicki
2020-01-11 6:12 ` [bpf PATCH v2 4/8] bpf: sockmap, skmsg helper overestimates push, pull, and pop bounds John Fastabend
2020-01-11 6:12 ` [bpf PATCH v2 5/8] bpf: sockmap/tls, msg_push_data may leave end mark in place John Fastabend
2020-01-11 6:12 ` [bpf PATCH v2 6/8] bpf: sockmap/tls, tls_sw can create a plaintext buf > encrypt buf John Fastabend
2020-01-11 6:12 ` [bpf PATCH v2 7/8] bpf: sockmap/tls, skmsg can have wrapped skmsg that needs extra chaining John Fastabend
2020-01-11 6:12 ` [bpf PATCH v2 8/8] bpf: sockmap/tls, fix pop data with SK_DROP return code John Fastabend
2020-01-15 22:37 ` [bpf PATCH v2 0/8] Fixes for sockmap/tls from more complex BPF progs Daniel Borkmann
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