linux-kernel - Re: [PATCH bpf v1] unix: fix an issue in unix_shutdown causing the other end read/write failures

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Date:   Mon, 4 Oct 2021 17:04:24 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Jiang Wang <jiang.wang@...edance.com>, bpf@...r.kernel.org
Cc:     cong.wang@...edance.com, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Eric Dumazet <edumazet@...gle.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Rao Shoaib <Rao.Shoaib@...cle.com>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Jakub Sitnicki <jakub@...udflare.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH bpf v1] unix: fix an issue in unix_shutdown causing the
 other end read/write failures

On 10/4/2021 4:25 PM, Jiang Wang wrote:
> Commit 94531cfcbe79 ("af_unix: Add unix_stream_proto for sockmap")
> sets unix domain socket peer state to TCP_CLOSE
> in unix_shutdown. This could happen when the local end is shutdown
> but the other end is not. Then the other end will get read or write
> failures which is not expected.
>
> Fix the issue by setting the local state to shutdown.
>
> Fixes: 94531cfcbe79 (af_unix: Add unix_stream_proto for sockmap)
> Suggested-by: Cong Wang <cong.wang@...edance.com>
> Reported-by: Casey Schaufler <casey@...aufler-ca.com>
> Signed-off-by: Jiang Wang <jiang.wang@...edance.com>

This patch looks like it has fixed the problem. My test cases
are now getting expected results consistently. Please add any
or all of:

Tested-by: Casey Schaufler <casey@...aufler-ca.com>
Reviewed-by: Casey Schaufler <casey@...aufler-ca.com>

> ---
>  net/unix/af_unix.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index efac5989edb5..0878ab86597b 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2882,6 +2882,9 @@ static int unix_shutdown(struct socket *sock, int mode)
>  
>  	unix_state_lock(sk);
>  	sk->sk_shutdown |= mode;
> +	if ((sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) &&
> +	    mode == SHUTDOWN_MASK)
> +		sk->sk_state = TCP_CLOSE;
>  	other = unix_peer(sk);
>  	if (other)
>  		sock_hold(other);
> @@ -2904,12 +2907,10 @@ static int unix_shutdown(struct socket *sock, int mode)
>  		other->sk_shutdown |= peer_mode;
>  		unix_state_unlock(other);
>  		other->sk_state_change(other);
> -		if (peer_mode == SHUTDOWN_MASK) {
> +		if (peer_mode == SHUTDOWN_MASK)
>  			sk_wake_async(other, SOCK_WAKE_WAITD, POLL_HUP);
> -			other->sk_state = TCP_CLOSE;
> -		} else if (peer_mode & RCV_SHUTDOWN) {
> +		else if (peer_mode & RCV_SHUTDOWN)
>  			sk_wake_async(other, SOCK_WAKE_WAITD, POLL_IN);
> -		}
>  	}
>  	if (other)
>  		sock_put(other);