netdev - Re: [PATCH v2 net] af_unix: Update unix_sk(sk)->oob_skb under sk_receive

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Message-ID: <20240510105400.32158-1-kuniyu@amazon.com>
Date: Fri, 10 May 2024 19:54:00 +0900
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <pabeni@...hat.com>
CC: <billy@...rlabs.sg>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <kuni1840@...il.com>, <kuniyu@...zon.com>,
	<netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net] af_unix: Update unix_sk(sk)->oob_skb under sk_receive_queue lock.

From: Paolo Abeni <pabeni@...hat.com>
Date: Fri, 10 May 2024 12:44:58 +0200
> On Fri, 2024-05-10 at 18:39 +0900, Kuniyuki Iwashima wrote:
> > diff --git a/net/unix/garbage.c b/net/unix/garbage.c
> > index 0104be9d4704..b87e48e2b51b 100644
> > --- a/net/unix/garbage.c
> > +++ b/net/unix/garbage.c
> > @@ -342,10 +342,12 @@ static void __unix_gc(struct work_struct *work)
> >  		scan_children(&u->sk, inc_inflight, &hitlist);
> >  
> >  #if IS_ENABLED(CONFIG_AF_UNIX_OOB)
> > +		spin_lock(&u->sk.sk_receive_queue.lock);
> >  		if (u->oob_skb) {
> > -			kfree_skb(u->oob_skb);
> > +			WARN_ON_ONCE(skb_unref(u->oob_skb));
> 
> Sorry for not asking this first, but it's not clear to me why the above
> change (just the 'WARN_ON_ONCE' introduction) is needed and if it's
> related to the addressed issue???

I think I added it to make it clear that here we don't actually free skb
and consistent with manage_oob().

But I don't have strong preference as it will be removed soon.