netdev - Re: [PATCH net] af_unix: Support POLLPRI for OOB.

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Date:   Mon, 14 Mar 2022 10:42:39 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rao Shoaib <Rao.Shoaib@...cle.com>
Cc:     Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net] af_unix: Support POLLPRI for OOB.


On 3/13/22 22:21, Kuniyuki Iwashima wrote:
> The commit 314001f0bf92 ("af_unix: Add OOB support") introduced OOB for
> AF_UNIX, but it lacks some changes for POLLPRI.  Let's add the missing
> piece.
>
> In the selftest, normal datagrams are sent followed by OOB data, so this
> commit replaces `POLLIN | POLLPRI` with just `POLLPRI` in the first test
> case.
>
> Fixes: 314001f0bf92 ("af_unix: Add OOB support")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
> ---
>   net/unix/af_unix.c                                  | 2 ++
>   tools/testing/selftests/net/af_unix/test_unix_oob.c | 6 +++---
>   2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index c19569819866..711d21b1c3e1 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -3139,6 +3139,8 @@ static __poll_t unix_poll(struct file *file, struct socket *sock, poll_table *wa
>   		mask |= EPOLLIN | EPOLLRDNORM;
>   	if (sk_is_readable(sk))
>   		mask |= EPOLLIN | EPOLLRDNORM;
> +	if (unix_sk(sk)->oob_skb)
> +		mask |= EPOLLPRI;


This adds another data-race, maybe add something to avoid another syzbot 
report ?


>   
>   	/* Connection-based need to check for termination and startup */
>   	if ((sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) &&
> diff --git a/tools/testing/selftests/net/af_unix/test_unix_oob.c b/tools/testing/selftests/net/af_unix/test_unix_oob.c
> index 3dece8b29253..b57e91e1c3f2 100644
> --- a/tools/testing/selftests/net/af_unix/test_unix_oob.c
> +++ b/tools/testing/selftests/net/af_unix/test_unix_oob.c
> @@ -218,10 +218,10 @@ main(int argc, char **argv)
>   
>   	/* Test 1:
>   	 * veriyf that SIGURG is
> -	 * delivered and 63 bytes are
> -	 * read and oob is '@'
> +	 * delivered, 63 bytes are
> +	 * read, oob is '@', and POLLPRI works.
>   	 */
> -	wait_for_data(pfd, POLLIN | POLLPRI);
> +	wait_for_data(pfd, POLLPRI);
>   	read_oob(pfd, &oob);
>   	len = read_data(pfd, buf, 1024);
>   	if (!signal_recvd || len != 63 || oob != '@') {