Acquire Giant conditionally in in_addmulti() and in_delmulti() based on

whether the interface being accessed is IFF_NEEDSGIANT or not.  This
avoids lock order reversals when calling into the interface ioctl
handler, which could potentially lead to deadlock.

The long term solution is to eliminate non-MPSAFE network drivers.

Discussed with:	jhb
MFC after:	1 week

1 files changed, 9 insertions, 0 deletions

diff --git a/sys/netinet/in.c b/sys/netinet/in.c
index 2eb5e94..0f44ba8 100644
--- a/sys/netinet/in.c
+++ b/sys/netinet/in.c
@@ -961,6 +961,7 @@ in_addmulti(ap, ifp)
 	struct sockaddr_in sin;
 	struct ifmultiaddr *ifma;
 
+	IFF_LOCKGIANT(ifp);
 	IN_MULTI_LOCK();
 	/*
 	 * Call generic routine to add membership or increment
@@ -974,6 +975,7 @@ in_addmulti(ap, ifp)
 	error = if_addmulti(ifp, (struct sockaddr *)&sin, &ifma);
 	if (error) {
 		IN_MULTI_UNLOCK();
+		IFF_UNLOCKGIANT(ifp);
 		return 0;
 	}
 
@@ -983,6 +985,7 @@ in_addmulti(ap, ifp)
 	 */
 	if (ifma->ifma_protospec != NULL) {
 		IN_MULTI_UNLOCK();
+		IFF_UNLOCKGIANT(ifp);
 		return ifma->ifma_protospec;
 	}
 
@@ -990,6 +993,7 @@ in_addmulti(ap, ifp)
 	    M_NOWAIT | M_ZERO);
 	if (inm == NULL) {
 		IN_MULTI_UNLOCK();
+		IFF_UNLOCKGIANT(ifp);
 		return (NULL);
 	}
 
@@ -1004,6 +1008,7 @@ in_addmulti(ap, ifp)
 	 */
 	igmp_joingroup(inm);
 	IN_MULTI_UNLOCK();
+	IFF_UNLOCKGIANT(ifp);
 	return (inm);
 }
 
@@ -1016,7 +1021,10 @@ in_delmulti(inm)
 {
 	struct ifmultiaddr *ifma;
 	struct in_multi my_inm;
+	struct ifnet *ifp;
 
+	ifp = inm->inm_ifp;
+	IFF_LOCKGIANT(ifp);
 	IN_MULTI_LOCK();
 	ifma = inm->inm_ifma;
 	my_inm.inm_ifp = NULL ; /* don't send the leave msg */
@@ -1036,6 +1044,7 @@ in_delmulti(inm)
 	if_delmulti(ifma->ifma_ifp, ifma->ifma_addr);
 	if (my_inm.inm_ifp != NULL)
 		igmp_leavegroup(&my_inm);
+	IFF_UNLOCKGIANT(ifp);
 	IN_MULTI_UNLOCK();
 }