5.4-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit eb0718fb3e97ad0d6f4529b810103451c90adf94 ]
unix_poll() and unix_dgram_poll() read sk->sk_state locklessly and calls unix_writable() which also reads sk->sk_state without holding unix_state_lock().
Let's use READ_ONCE() in unix_poll() and unix_dgram_poll() and pass it to unix_writable().
While at it, we remove TCP_SYN_SENT check in unix_dgram_poll() as that state does not exist for AF_UNIX socket since the code was added.
Fixes: 1586a5877db9 ("af_unix: do not report POLLOUT on listeners") Fixes: 3c73419c09a5 ("af_unix: fix 'poll for write'/ connected DGRAM sockets") Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/unix/af_unix.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 8ab1e2a781195..73cc992bed880 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -449,9 +449,9 @@ static int unix_dgram_peer_wake_me(struct sock *sk, struct sock *other) return 0; }
-static int unix_writable(const struct sock *sk) +static int unix_writable(const struct sock *sk, unsigned char state) { - return sk->sk_state != TCP_LISTEN && + return state != TCP_LISTEN && (refcount_read(&sk->sk_wmem_alloc) << 2) <= sk->sk_sndbuf; }
@@ -460,7 +460,7 @@ static void unix_write_space(struct sock *sk) struct socket_wq *wq;
rcu_read_lock(); - if (unix_writable(sk)) { + if (unix_writable(sk, READ_ONCE(sk->sk_state))) { wq = rcu_dereference(sk->sk_wq); if (skwq_has_sleeper(wq)) wake_up_interruptible_sync_poll(&wq->wait, @@ -2678,12 +2678,14 @@ static int unix_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned lon static __poll_t unix_poll(struct file *file, struct socket *sock, poll_table *wait) { struct sock *sk = sock->sk; + unsigned char state; __poll_t mask; u8 shutdown;
sock_poll_wait(file, sock, wait); mask = 0; shutdown = READ_ONCE(sk->sk_shutdown); + state = READ_ONCE(sk->sk_state);
/* exceptional events? */ if (sk->sk_err) @@ -2699,14 +2701,14 @@ static __poll_t unix_poll(struct file *file, struct socket *sock, poll_table *wa
/* Connection-based need to check for termination and startup */ if ((sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) && - sk->sk_state == TCP_CLOSE) + state == TCP_CLOSE) mask |= EPOLLHUP;
/* * we set writable also when the other side has shut down the * connection. This prevents stuck sockets. */ - if (unix_writable(sk)) + if (unix_writable(sk, state)) mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;
return mask; @@ -2717,12 +2719,14 @@ static __poll_t unix_dgram_poll(struct file *file, struct socket *sock, { struct sock *sk = sock->sk, *other; unsigned int writable; + unsigned char state; __poll_t mask; u8 shutdown;
sock_poll_wait(file, sock, wait); mask = 0; shutdown = READ_ONCE(sk->sk_shutdown); + state = READ_ONCE(sk->sk_state);
/* exceptional events? */ if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) @@ -2739,19 +2743,14 @@ static __poll_t unix_dgram_poll(struct file *file, struct socket *sock, mask |= EPOLLIN | EPOLLRDNORM;
/* Connection-based need to check for termination and startup */ - if (sk->sk_type == SOCK_SEQPACKET) { - if (sk->sk_state == TCP_CLOSE) - mask |= EPOLLHUP; - /* connection hasn't started yet? */ - if (sk->sk_state == TCP_SYN_SENT) - return mask; - } + if (sk->sk_type == SOCK_SEQPACKET && state == TCP_CLOSE) + mask |= EPOLLHUP;
/* No write status requested, avoid expensive OUT tests. */ if (!(poll_requested_events(wait) & (EPOLLWRBAND|EPOLLWRNORM|EPOLLOUT))) return mask;
- writable = unix_writable(sk); + writable = unix_writable(sk, state); if (writable) { unix_state_lock(sk);