1 files changed, 4 insertions, 2 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 1237d5d037d8..5fd8ec895c8b 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1070,8 +1070,10 @@ static int ipv6_get_saddr_eval(struct net *net,
                 break;
         case IPV6_SADDR_RULE_PREFIX:
                 /* Rule 8: Use longest matching prefix */
-                score->matchlen = ret = ipv6_addr_diff(&score->ifa->addr,
-                                                       dst->addr);
+                ret = ipv6_addr_diff(&score->ifa->addr, dst->addr);
+                if (ret > score->ifa->prefix_len)
+                        ret = score->ifa->prefix_len;
+                score->matchlen = ret;
                 break;
         default:
                 ret = 0;