m_pullup(9) regression

[Martin Pieuchot]

semarie exposed a bug in m_pullup(9) while testing my diff to
automatically create lo(4) interfaces per rdomain.

In the block below ``m'' is dereferenced without being previously set.

Is the diff below correct?

Index: kern/uipc_mbuf.c
===================================================================
RCS file: /cvs/src/sys/kern/uipc_mbuf.c,v
retrieving revision 1.237
diff -u -p -r1.237 uipc_mbuf.c
--- kern/uipc_mbuf.c    27 Oct 2016 03:29:55 -0000      1.237
+++ kern/uipc_mbuf.c    8 Nov 2016 09:57:06 -0000
@@ -896,7 +896,7 @@ m_pullup(struct mbuf *n, int len)
                if (len > tail - mtod(n, caddr_t)) {
                        /* need to memmove to make space at the end */
                        memmove(head, mtod(n, caddr_t), n->m_len);
-                       m->m_data = head;
+                       n->m_data = head;
                }
 
                len -= n->m_len;