[IPV4]: fix IPv4 leave-group group matching

        This patch fixes the multicast group matching for 
IP_DROP_MEMBERSHIP, similar to the IP_ADD_MEMBERSHIP fix in a prior
patch. Groups are identifiedby <group address,interface> and including
the interface address in the match will fail if a leave-group is done
by address when the join was done by index, or if different addresses
on the same interface are used in the join and leave.

Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 12 deletions

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 7af3146939dc..5088f90835ae 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1687,24 +1687,25 @@ int ip_mc_leave_group(struct sock *sk, struct ip_mreqn *imr)
 {
         struct inet_sock *inet = inet_sk(sk);
         struct ip_mc_socklist *iml, **imlp;
+        struct in_device *in_dev;
+        u32 group = imr->imr_multiaddr.s_addr;
+        u32 ifindex;
 
         rtnl_lock();
+        in_dev = ip_mc_find_dev(imr);
+        if (!in_dev) {
+                rtnl_unlock();
+                return -ENODEV;
+        }
+        ifindex = imr->imr_ifindex;
         for (imlp = &inet->mc_list; (iml = *imlp) != NULL; imlp = &iml->next) {
-                if (iml->multi.imr_multiaddr.s_addr==imr->imr_multiaddr.s_addr &&
-                    iml->multi.imr_address.s_addr==imr->imr_address.s_addr &&
-                    (!imr->imr_ifindex || iml->multi.imr_ifindex==imr->imr_ifindex)) {
-                        struct in_device *in_dev;
-
-                        in_dev = inetdev_by_index(iml->multi.imr_ifindex);
-                        if (in_dev)
-                                (void) ip_mc_leave_src(sk, iml, in_dev);
+                if (iml->multi.imr_multiaddr.s_addr == group &&
+                    iml->multi.imr_ifindex == ifindex) {
+                        (void) ip_mc_leave_src(sk, iml, in_dev);
 
                         *imlp = iml->next;
 
-                        if (in_dev) {
-                                ip_mc_dec_group(in_dev, imr->imr_multiaddr.s_addr);
-                                in_dev_put(in_dev);
-                        }
+                        ip_mc_dec_group(in_dev, group);
                         rtnl_unlock();
                         sock_kfree_s(sk, iml, sizeof(*iml));
                         return 0;