[src/trunk]: src/sys/netinet6 Plug a race condition on accessing i6mm_maddr

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3a6af296276c
branches:  trunk
changeset: 822123:3a6af296276c
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Thu Mar 02 09:48:20 2017 +0000

description:
Plug a race condition on accessing i6mm_maddr

diffstat:

 sys/netinet6/in6.c     |   7 ++++---
 sys/netinet6/in6_var.h |   3 ++-
 sys/netinet6/mld6.c    |  26 ++++++++++++++++++++++----
 3 files changed, 28 insertions(+), 8 deletions(-)

diffs (103 lines):

diff -r 6707fbb67df4 -r 3a6af296276c sys/netinet6/in6.c
--- a/sys/netinet6/in6.c        Thu Mar 02 09:16:46 2017 +0000
+++ b/sys/netinet6/in6.c        Thu Mar 02 09:48:20 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: in6.c,v 1.243 2017/03/02 09:16:46 ozaki-r Exp $        */
+/*     $NetBSD: in6.c,v 1.244 2017/03/02 09:48:20 ozaki-r Exp $        */
 /*     $KAME: in6.c,v 1.198 2001/07/18 09:12:38 itojun Exp $   */
 
 /*
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: in6.c,v 1.243 2017/03/02 09:16:46 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: in6.c,v 1.244 2017/03/02 09:48:20 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -1462,10 +1462,11 @@
 {
        struct  in6_ifaddr *ia;
 
+       KASSERT(in6_multi_locked(RW_WRITER));
+
        mutex_enter(&in6_ifaddr_lock);
        IN6_ADDRLIST_WRITER_FOREACH(ia) {
                struct in6_multi_mship *imm;
-               /* XXX imm isn't safe? */
                LIST_FOREACH(imm, &ia->ia6_memberships, i6mm_chain) {
                        if (imm->i6mm_maddr == in6m)
                                imm->i6mm_maddr = NULL;
diff -r 6707fbb67df4 -r 3a6af296276c sys/netinet6/in6_var.h
--- a/sys/netinet6/in6_var.h    Thu Mar 02 09:16:46 2017 +0000
+++ b/sys/netinet6/in6_var.h    Thu Mar 02 09:48:20 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: in6_var.h,v 1.96 2017/03/02 09:16:46 ozaki-r Exp $     */
+/*     $NetBSD: in6_var.h,v 1.97 2017/03/02 09:48:20 ozaki-r Exp $     */
 /*     $KAME: in6_var.h,v 1.81 2002/06/08 11:16:51 itojun Exp $        */
 
 /*
@@ -683,6 +683,7 @@
 
 void   in6_multi_lock(int);
 void   in6_multi_unlock(void);
+bool   in6_multi_locked(int);
 struct in6_multi *
        in6_lookup_multi(const struct in6_addr *, const struct ifnet *);
 bool   in6_multi_group(const struct in6_addr *, const struct ifnet *);
diff -r 6707fbb67df4 -r 3a6af296276c sys/netinet6/mld6.c
--- a/sys/netinet6/mld6.c       Thu Mar 02 09:16:46 2017 +0000
+++ b/sys/netinet6/mld6.c       Thu Mar 02 09:48:20 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mld6.c,v 1.87 2017/03/02 09:16:46 ozaki-r Exp $        */
+/*     $NetBSD: mld6.c,v 1.88 2017/03/02 09:48:20 ozaki-r Exp $        */
 /*     $KAME: mld6.c,v 1.25 2001/01/16 14:14:18 itojun Exp $   */
 
 /*
@@ -102,7 +102,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: mld6.c,v 1.87 2017/03/02 09:16:46 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: mld6.c,v 1.88 2017/03/02 09:48:20 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -915,6 +915,20 @@
        rw_exit(&in6_multilock);
 }
 
+bool
+in6_multi_locked(int op)
+{
+
+       switch (op) {
+       case RW_READER:
+               return rw_read_held(&in6_multilock);
+       case RW_WRITER:
+               return rw_write_held(&in6_multilock);
+       default:
+               return rw_lock_held(&in6_multilock);
+       }
+}
+
 struct in6_multi_mship *
 in6_joingroup(struct ifnet *ifp, struct in6_addr *addr, 
        int *errorp, int timer)
@@ -939,9 +953,13 @@
 int
 in6_leavegroup(struct in6_multi_mship *imm)
 {
+       struct in6_multi *in6m;
 
-       if (imm->i6mm_maddr) {
-               in6_delmulti(imm->i6mm_maddr);
+       rw_enter(&in6_multilock, RW_READER);
+       in6m = imm->i6mm_maddr;
+       rw_exit(&in6_multilock);
+       if (in6m != NULL) {
+               in6_delmulti(in6m);
        }
        free(imm, M_IPMADDR);
        return 0;