[IPV6]: Fix dangling references on error in fib6_add().

Fixes bugzilla #8895

If a super-tree leaf has 'rt' assigned to it and we
get an error from fib6_add_rt2node(), we'll leave
a reference to 'rt' in pn->leaf and then do an
unconditional dst_free().

We should prune such references.

Based upon a report by Vincent Perrier.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index b3f6e03c454c..50f3f8f8a59b 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -772,6 +772,10 @@ out:
                  * If fib6_add_1 has cleared the old leaf pointer in the
                  * super-tree leaf node we have to find a new one for it.
                  */
+                if (pn != fn && pn->leaf == rt) {
+                        pn->leaf = NULL;
+                        atomic_dec(&rt->rt6i_ref);
+                }
                 if (pn != fn && !pn->leaf && !(pn->fn_flags & RTN_RTINFO)) {
                         pn->leaf = fib6_find_prefix(info->nl_net, pn);
 #if RT6_DEBUG >= 2