netdev - Re: [PATCH net] netfilter: nfnetlink_queue: acquire rcu_read_lock() in instance_destroy

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Message-ID: <CANn89iLA=SfNB6c65FG2DCD90NZLdzPBcA2a0VDhx+vsnXKnww@mail.gmail.com>
Date: Wed, 15 May 2024 15:42:47 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Florian Westphal <fw@...len.de>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Pablo Neira Ayuso <pablo@...filter.org>, 
	Jozsef Kadlecsik <kadlec@...filter.org>, netdev@...r.kernel.org, 
	netfilter-devel@...r.kernel.org, coreteam@...filter.org, 
	eric.dumazet@...il.com, syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] netfilter: nfnetlink_queue: acquire rcu_read_lock()
 in instance_destroy_rcu()

On Wed, May 15, 2024 at 3:39 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Wed, May 15, 2024 at 3:27 PM Florian Westphal <fw@...len.de> wrote:
> >
> > Eric Dumazet <edumazet@...gle.com> wrote:
> > > diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
> > > index 00f4bd21c59b419e96794127693c21ccb05e45b0..f1c31757e4969e8f975c7a1ebbc3b96148ec9724 100644
> > > --- a/net/netfilter/nfnetlink_queue.c
> > > +++ b/net/netfilter/nfnetlink_queue.c
> > > @@ -169,7 +169,9 @@ instance_destroy_rcu(struct rcu_head *head)
> > >       struct nfqnl_instance *inst = container_of(head, struct nfqnl_instance,
> > >                                                  rcu);
> > >
> > > +     rcu_read_lock();
> > >       nfqnl_flush(inst, NULL, 0);
> > > +     rcu_read_unlock();
> >
> > That works too.  I sent a different patch for the same issue yesterday:
> >
> > https://patchwork.ozlabs.org/project/netfilter-devel/patch/20240514103133.2784-1-fw@strlen.de/
> >
> > If you prefer Erics patch thats absolutely fine with me, I'll rebase in
> > that case to keep the selftest around.
>
> I missed your patch, otherwise I would have done nothing ;)
>
> I saw the recent changes about nf_reinject() and tried to have a patch
> that would be easily backported without conflicts.
>
> Do you think the splat is caused by recent changes, or is it simply
> syzbot getting smarter ?

(It took me a fair amount of time to find a Fixes: tag, this is why I am asking)