netdev - Re: [PATCH v5] af_unix: Read with MSG_PEEK loops if the first unread byte is OOB

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Date: Wed, 5 Jun 2024 14:21:19 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <Rao.Shoaib@...cle.com>
CC: <pabeni@...hat.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <kuniyu@...zon.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v5] af_unix: Read with MSG_PEEK loops if the first unread byte is OOB

From: Paolo Abeni <pabeni@...hat.com>
Date: Tue, 21 May 2024 13:11:52 +0200
> On Thu, 2024-05-16 at 16:16 -0700, Rao Shoaib wrote:
> > Read with MSG_PEEK flag loops if the first byte to read is an OOB byte.
> > commit 22dd70eb2c3d ("af_unix: Don't peek OOB data without MSG_OOB.")
> > addresses the loop issue but does not address the issue that no data
> > beyond OOB byte can be read.
> > 
> > > > > from socket import *
> > > > > c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
> > > > > c1.send(b'a', MSG_OOB)
> > 1
> > > > > c1.send(b'b')
> > 1
> > > > > c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
> > b'b'
> > 
> > > > > from socket import *
> > > > > c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
> > > > > c2.setsockopt(SOL_SOCKET, SO_OOBINLINE, 1)
> > > > > c1.send(b'a', MSG_OOB)
> > 1
> > > > > c1.send(b'b')
> > 1
> > > > > c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
> > b'a'
> > > > > c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
> > b'a'
> > > > > c2.recv(1, MSG_DONTWAIT)
> > b'a'
> > > > > c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
> > b'b'
> > > > > 
> > 
> > Fixes: 314001f0bf92 ("af_unix: Add OOB support")
> > Signed-off-by: Rao Shoaib <Rao.Shoaib@...cle.com>
> > ---
> >  net/unix/af_unix.c | 20 ++++++++++----------
> >  1 file changed, 10 insertions(+), 10 deletions(-)
> > 
> > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> > index fa906ec5e657..6e5ef44640ea 100644
> > --- a/net/unix/af_unix.c
> > +++ b/net/unix/af_unix.c
> > @@ -2612,19 +2612,19 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
> >  		if (skb == u->oob_skb) {
> >  			if (copied) {
> >  				skb = NULL;
> > -			} else if (sock_flag(sk, SOCK_URGINLINE)) {
> > -				if (!(flags & MSG_PEEK)) {
> > +			} else if (!(flags & MSG_PEEK)) {
> > +				if (sock_flag(sk, SOCK_URGINLINE)) {
> >  					WRITE_ONCE(u->oob_skb, NULL);
> >  					consume_skb(skb);
> > +				} else {
> > +					skb_unlink(skb, &sk->sk_receive_queue);
> > +					WRITE_ONCE(u->oob_skb, NULL);
> > +					if (!WARN_ON_ONCE(skb_unref(skb)))
> > +						kfree_skb(skb);
> > +					skb = skb_peek(&sk->sk_receive_queue);
> >  				}
> > -			} else if (flags & MSG_PEEK) {
> > -				skb = NULL;
> > -			} else {
> > -				skb_unlink(skb, &sk->sk_receive_queue);
> > -				WRITE_ONCE(u->oob_skb, NULL);
> > -				if (!WARN_ON_ONCE(skb_unref(skb)))
> > -					kfree_skb(skb);
> > -				skb = skb_peek(&sk->sk_receive_queue);
> > +			} else if (!sock_flag(sk, SOCK_URGINLINE)) {
> > +				skb = skb_peek_next(skb, &sk->sk_receive_queue);
> >  			}
> >  		}
> >  	}
> 
> Does not apply cleanly anymore after commit 9841991a446c ("af_unix:
> Update unix_sk(sk)->oob_skb under sk_receive_queue lock."), please
> rebase, thanks!

Hi Rao,

Do you have time to respin v6 or do you mind if I rebase it and post v6 ?
I have some patches for net-next on top of this fix.

Thanks