af_unix: do not report POLLOUT on listeners

Eric Dumazet · davem330 · commit 1586a5877db9 · 2015-10-25T06:37:45.000-07:00
poll(POLLOUT) on a listener should not report fd is ready for
a write().

This would break some applications using poll() and pfd.events = -1,
as they would not block in poll()

Signed-off-by: Eric Dumazet &lt;edumazet@google.com&gt;
Reported-by: Alan Burlison &lt;Alan.Burlison@oracle.com&gt;
Tested-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
@@ -326,9 +326,10 @@ static struct sock *unix_find_socket_byinode(struct inode *i)
 	return s;
 }
 
-static inline int unix_writable(struct sock *sk)
+static int unix_writable(const struct sock *sk)
 {
-	return (atomic_read(&sk->sk_wmem_alloc) << 2) <= sk->sk_sndbuf;
+	return sk->sk_state != TCP_LISTEN &&
+	       (atomic_read(&sk->sk_wmem_alloc) << 2) <= sk->sk_sndbuf;
 }
 
 static void unix_write_space(struct sock *sk)

Original file line number	Diff line number	Diff line change
`@@ -326,9 +326,10 @@ static struct sock unix_find_socket_byinode(struct inode i)`
`326`	`326`	`return s;`
`327`	`327`	`}`
`328`	`328`
`329`		`-static inline int unix_writable(struct sock *sk)`
	`329`	`+static int unix_writable(const struct sock *sk)`
`330`	`330`	`{`
`331`		`- return (atomic_read(&sk->sk_wmem_alloc) << 2) <= sk->sk_sndbuf;`
	`331`	`+ return sk->sk_state != TCP_LISTEN &&`
	`332`	`+ (atomic_read(&sk->sk_wmem_alloc) << 2) <= sk->sk_sndbuf;`
`332`	`333`	`}`
`333`	`334`
`334`	`335`	`static void unix_write_space(struct sock *sk)`