net: netlink: Fix multicast group storage allocation for families with more than one groups

Multicast groups are stored in global buffer. Check for needed buffer size
incorrectly compares buffer size to first id for family. This means that
for families with more than one mcast id one may allocate too small buffer
and end up writing rest of the groups to some unallocated memory. Fix the
buffer size check to compare allocated space to last mcast id for the
family.

Tested on ARM using kernel 3.14

Signed-off-by: Matti Vaittinen <matti.vaittinen@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index bc0e504..a992083 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -185,7 +185,7 @@ static int genl_allocate_reserve_groups(int n_groups, int *first_id)
 			}
 		}
 
-		if (id >= mc_groups_longs * BITS_PER_LONG) {
+		if (id + n_groups >= mc_groups_longs * BITS_PER_LONG) {
 			unsigned long new_longs = mc_groups_longs +
 						  BITS_TO_LONGS(n_groups);
 			size_t nlen = new_longs * sizeof(unsigned long);