af_unix: Set sk->sk_state under unix_state_lock() for truly disconencted peer.
When a SOCK_DGRAM socket connect()s to another socket, the both sockets'
sk->sk_state are changed to TCP_ESTABLISHED so that we can register them
to BPF SOCKMAP.
When the socket disconnects from the peer by connect(AF_UNSPEC), the state
is set back to TCP_CLOSE.
Then, the peer's state is also set to TCP_CLOSE, but the update is done
locklessly and unconditionally.
Let's say socket A connect()ed to B, B connect()ed to C, and A disconnects
from B.
After the first two connect()s, all three sockets' sk->sk_state are
TCP_ESTABLISHED:
$ ss -xa
Netid State Recv-Q Send-Q Local Address:Port Peer Address:PortProcess
u_dgr ESTAB 0 0 @A 641 * 642
u_dgr ESTAB 0 0 @B 642 * 643
u_dgr ESTAB 0 0 @C 643 * 0
And after the disconnect, B's state is TCP_CLOSE even though it's still
connected to C and C's state is TCP_ESTABLISHED.
$ ss -xa
Netid State Recv-Q Send-Q Local Address:Port Peer Address:PortProcess
u_dgr UNCONN 0 0 @A 641 * 0
u_dgr UNCONN 0 0 @B 642 * 643
u_dgr ESTAB 0 0 @C 643 * 0
In this case, we cannot register B to SOCKMAP.
So, when a socket disconnects from the peer, we should not set TCP_CLOSE to
the peer if the peer is connected to yet another socket, and this must be
done under unix_state_lock().
Note that we use WRITE_ONCE() for sk->sk_state as there are many lockless
readers. These data-races will be fixed in the following patches.
Fixes: 83301b5367
("af_unix: Set TCP_ESTABLISHED for datagram sockets too")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
parent
b0c9a26435
commit
26bfb8b570
1 changed files with 8 additions and 2 deletions
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@ -570,7 +570,6 @@ static void unix_dgram_disconnected(struct sock *sk, struct sock *other)
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sk_error_report(other);
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}
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}
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other->sk_state = TCP_CLOSE;
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}
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static void unix_sock_destructor(struct sock *sk)
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@ -1424,8 +1423,15 @@ restart:
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unix_state_double_unlock(sk, other);
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if (other != old_peer)
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if (other != old_peer) {
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unix_dgram_disconnected(sk, old_peer);
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unix_state_lock(old_peer);
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if (!unix_peer(old_peer))
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WRITE_ONCE(old_peer->sk_state, TCP_CLOSE);
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unix_state_unlock(old_peer);
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}
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sock_put(old_peer);
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} else {
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unix_peer(sk) = other;
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