Index: sys/net/if.c
===================================================================
--- sys/net/if.c
+++ sys/net/if.c
@@ -472,11 +472,24 @@
 {
 	struct ifnet *ifp, *nifp;
 
+	/*
+	 * We need to protect our access to the V_ifnet tailq. Ordinarily we'd
+	 * enter NET_EPOCH, but that's not possible, because if_vmove() calls
+	 * if_detach_internal(), which waits for NET_EPOCH callbacks to
+	 * complete. We can't do that from within NET_EPOCH.
+	 *
+	 * However, we can also use the IFNET_xLOCK, which is the V_ifnet
+	 * read/write lock. We take this lock from within if_vmove() as well,
+	 * but it's a recursive lock, so that's safe. We do have to take the
+	 * write lock, because we need the write lock in if_vmove().
+	 */
+	IFNET_WLOCK();
 	/* Return all inherited interfaces to their parent vnets. */
 	CK_STAILQ_FOREACH_SAFE(ifp, &V_ifnet, if_link, nifp) {
 		if (ifp->if_home_vnet != ifp->if_vnet)
 			if_vmove(ifp, ifp->if_home_vnet);
 	}
+	IFNET_WUNLOCK();
 }
 VNET_SYSUNINIT(vnet_if_return, SI_SUB_VNET_DONE, SI_ORDER_ANY,
     vnet_if_return, NULL);
Index: sys/net/if_var.h
===================================================================
--- sys/net/if_var.h
+++ sys/net/if_var.h
@@ -595,23 +595,10 @@
 
 extern	struct sx ifnet_sxlock;
 
-#define	IFNET_WLOCK() do {						\
-	sx_xlock(&ifnet_sxlock);					\
-} while (0)
-
-#define	IFNET_WUNLOCK() do {						\
-	sx_xunlock(&ifnet_sxlock);					\
-} while (0)
-
-/*
- * To assert the ifnet lock, you must know not only whether it's for read or
- * write, but also whether it was acquired with sleep support or not.
- */
-#define	IFNET_RLOCK_ASSERT()		sx_assert(&ifnet_sxlock, SA_SLOCKED)
-#define	IFNET_WLOCK_ASSERT() do {					\
-	sx_assert(&ifnet_sxlock, SA_XLOCKED);				\
-} while (0)
-
+#define	IFNET_WLOCK()		sx_xlock(&ifnet_sxlock)
+#define	IFNET_WUNLOCK()		sx_xunlock(&ifnet_sxlock)
+#define	IFNET_RLOCK_ASSERT()	sx_assert(&ifnet_sxlock, SA_SLOCKED)
+#define	IFNET_WLOCK_ASSERT()	sx_assert(&ifnet_sxlock, SA_XLOCKED)
 #define	IFNET_RLOCK()		sx_slock(&ifnet_sxlock)
 #define	IFNET_RUNLOCK()		sx_sunlock(&ifnet_sxlock)