linux-kernel - Re: [PATCH net 03/13] mptcp: fix lockless access in subflow ULP diag

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Date: Tue, 20 Feb 2024 18:33:20 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, mptcp@...ts.linux.dev, 
 Mat Martineau <martineau@...nel.org>, Geliang Tang <geliang@...nel.org>,
 "David S. Miller" <davem@...emloft.net>,  Jakub Kicinski <kuba@...nel.org>,
 Davide Caratti <dcaratti@...hat.com>, Shuah Khan <shuah@...nel.org>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, stable@...r.kernel.org, Boris Pismenny
 <borisp@...dia.com>, John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH net 03/13] mptcp: fix lockless access in subflow ULP diag

On Mon, 2024-02-19 at 19:33 +0100, Eric Dumazet wrote:
> On Mon, Feb 19, 2024 at 7:04 PM Paolo Abeni <pabeni@...hat.com> wrote:
> > Thanks for the head-up. This later option looks preferable, to avoid
> > quit a bit of noise with _ONCE annotation. Is there a syzkaller splat I
> > could look at? if it landed on the ML, I missed it.
> > 
> 
> Not landed yet, here is the splat :
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.8.0-rc4-syzkaller-00212-g40b9385dd8e6 #0 Not tainted
> ------------------------------------------------------
> syz-executor.2/24141 is trying to acquire lock:
> ffff888045870130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at:
> tcp_diag_put_ulp net/ipv4/tcp_diag.c:100 [inline]
> ffff888045870130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at:
> tcp_diag_get_aux+0x738/0x830 net/ipv4/tcp_diag.c:137
> 
> but task is already holding lock:
> ffffc9000135e488 (&h->lhash2[i].lock){+.+.}-{2:2}, at: spin_lock
> include/linux/spinlock.h:351 [inline]
> ffffc9000135e488 (&h->lhash2[i].lock){+.+.}-{2:2}, at:
> inet_diag_dump_icsk+0x39f/0x1f80 net/ipv4/inet_diag.c:1038

[Sorry for the latency]. Yes it looks like that checking the listener
status will work. I can test and send the formal patch - with the due
credits! - or do you prefer otherwise?

Thanks!

Paolo