From: mpi <mpi@openbsd.org>
Date: Tue, 30 May 2017 06:42:13 +0000 (+0000)
Subject: Clear the internal table used by if_get(9) and sleep until all
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=563e030e0bfeebeff8d96a7df7fcb228c1de5c40;p=openbsd

Clear the internal table used by if_get(9) and sleep until all
remaining ifp references are released *without* the NET_LOCK().

It's safe to do so because the KERNEL_LOCK() serializes accesses
to ``if_map''.

More importantly this fix possible deadlocks between if_get() and
the NET_LOCK().  It is now possible to call them in whatever order.

ok visa@, dlg@
---

diff --git a/sys/net/if.c b/sys/net/if.c
index d519ddcfeba..29ec9034760 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if.c,v 1.500 2017/05/29 06:08:21 mpi Exp $	*/
+/*	$OpenBSD: if.c,v 1.501 2017/05/30 06:42:13 mpi Exp $	*/
 /*	$NetBSD: if.c,v 1.35 1996/05/07 05:26:04 thorpej Exp $	*/
 
 /*
@@ -1014,11 +1014,11 @@ if_detach(struct ifnet *ifp)
 
 	ifq_clr_oactive(&ifp->if_snd);
 
-	NET_LOCK(s);
-	s2 = splnet();
 	/* Other CPUs must not have a reference before we start destroying. */
 	if_idxmap_remove(ifp);
 
+	NET_LOCK(s);
+	s2 = splnet();
 	ifp->if_qstart = if_detached_qstart;
 	ifp->if_ioctl = if_detached_ioctl;
 	ifp->if_watchdog = NULL;