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:   Tue, 5 Oct 2021 22:17:37 +0000
From:   Song Liu <songliubraving@...com>
To:     Casey Schaufler <casey@...aufler-ca.com>
CC:     Jiang Wang <jiang.wang@...edance.com>, bpf <bpf@...r.kernel.org>,
        "Cong Wang" <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 Lau" <kafai@...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" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf v1] unix: fix an issue in unix_shutdown causing the
 other end read/write failures



> On Oct 4, 2021, at 5:04 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
> 
> 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>

Acked-by: Song Liu <songliubraving@...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);