Extend the scope of socket lock in soo_stat()

[Martin Pieuchot]

`so_state' and `so_rcv' need to be checked atomically, so extend the
scope of the lock.

ok?

Index: kern/sys_socket.c
===================================================================
RCS file: /cvs/src/sys/kern/sys_socket.c,v
retrieving revision 1.30
diff -u -p -r1.30 sys_socket.c
--- kern/sys_socket.c   22 Feb 2017 10:20:21 -0000      1.30
+++ kern/sys_socket.c   18 Jul 2017 06:41:10 -0000
@@ -180,14 +180,13 @@ soo_stat(struct file *fp, struct stat *u
 
        memset(ub, 0, sizeof (*ub));
        ub->st_mode = S_IFSOCK;
-       if ((so->so_state & SS_CANTRCVMORE) == 0 ||
-           so->so_rcv.sb_cc != 0)
+       s = solock(so);
+       if ((so->so_state & SS_CANTRCVMORE) == 0 || so->so_rcv.sb_cc != 0)
                ub->st_mode |= S_IRUSR | S_IRGRP | S_IROTH;
        if ((so->so_state & SS_CANTSENDMORE) == 0)
                ub->st_mode |= S_IWUSR | S_IWGRP | S_IWOTH;
        ub->st_uid = so->so_euid;
        ub->st_gid = so->so_egid;
-       s = solock(so);
        (void) ((*so->so_proto->pr_usrreq)(so, PRU_SENSE,
            (struct mbuf *)ub, NULL, NULL, p));
        sounlock(s);