FREF() earlier in getsock()

[Martin Pieuchot]

Here's a diff to move FREF() just after fd_getfile() in getsock().

As explained recently [0], I'd like to make sure all operations
manipulating a 'struct file *' do so with a properly refcounted
element.

[0] https://marc.info/?l=openbsd-tech&m=152214234530708&w=2

Ok?

Index: kern/uipc_syscalls.c
===================================================================
RCS file: /cvs/src/sys/kern/uipc_syscalls.c,v
retrieving revision 1.167
diff -u -p -r1.167 uipc_syscalls.c
--- kern/uipc_syscalls.c        21 Feb 2018 09:30:02 -0000      1.167
+++ kern/uipc_syscalls.c        27 Mar 2018 09:19:37 -0000
@@ -1160,9 +1160,11 @@ getsock(struct proc *p, int fdes, struct
 
        if ((fp = fd_getfile(p->p_fd, fdes)) == NULL)
                return (EBADF);
-       if (fp->f_type != DTYPE_SOCKET)
-               return (ENOTSOCK);
        FREF(fp);
+       if (fp->f_type != DTYPE_SOCKET) {
+               FRELE(fp, p);
+               return (ENOTSOCK);
+       }
        *fpp = fp;
 
        return (0);