netdev - Re: [PATCH v6] af_unix: Read with MSG_PEEK loops if the first unread byte is OOB

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Date: Tue, 11 Jun 2024 09:14:56 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <rao.shoaib@...cle.com>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<kuniyu@...zon.com>, <netdev@...r.kernel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH v6] af_unix: Read with MSG_PEEK loops if the first unread byte is OOB

From: Rao Shoaib <Rao.Shoaib@...cle.com>
Date: Tue, 11 Jun 2024 01:46:39 -0700
> 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")
>

No newline is needed here, but I think it isn't worth v7
and can be fixed during merge.


> Signed-off-by: Rao Shoaib <Rao.Shoaib@...cle.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>

Thanks!


> ---
>  net/unix/af_unix.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 80846279de9f..5e695a9a609c 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2625,18 +2625,18 @@ 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);
> +					unlinked_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);
> -				unlinked_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);
>  			}
>  		}
>  
> -- 
> 2.39.3