From: Wei Wang <wei...@google.com>
After rwlock is replaced with rcu and spinlock, fib6_lookup() could
potentially return an intermediate node if other thread is doing
fib6_del() on a route which is the only route on the node so that
fib6_repair_tree() will be called on this node and potentially assigns
fn->leaf to the its child's fn->leaf.
In order to detect this situation in rt6_select(), we have to check if
fn->fn_bit is consistent with the key length stored in the route. And
depending on if the fn is in the subtree or not, the key is either
rt->rt6i_dst or rt->rt6i_src.
If any inconsistency is found, that means the node no longer holds valid
routes in it. So net->ipv6.ip6_null_entry is returned.
Signed-off-by: Wei Wang <wei...@google.com>
Signed-off-by: Martin KaFai Lau <ka...@fb.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
---
net/ipv6/route.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 05dc450af441..24b80f43bbfb 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -755,6 +755,7 @@ static struct rt6_info *rt6_select(struct net *net, struct
fib6_node *fn,
struct rt6_info *leaf = fn->leaf;
struct rt6_info *match, *rt0;
bool do_rr = false;
+ int key_plen;
if (!leaf)
return net->ipv6.ip6_null_entry;
@@ -763,6 +764,19 @@ static struct rt6_info *rt6_select(struct net *net, struct
fib6_node *fn,
if (!rt0)
fn->rr_ptr = rt0 = leaf;
+ /* Double check to make sure fn is not an intermediate node
+ * and fn->leaf does not points to its child's leaf
+ * (This might happen if all routes under fn are deleted from
+ * the tree and fib6_repair_tree() is called on the node.)
+ */
+ key_plen = rt0->rt6i_dst.plen;
+#ifdef CONFIG_IPV6_SUBTREES
+ if (rt0->rt6i_src.plen)
+ key_plen = rt0->rt6i_src.plen;
+#endif
+ if (fn->fn_bit != key_plen)
+ return net->ipv6.ip6_null_entry;
+
match = find_rr_leaf(fn, leaf, rt0, rt0->rt6i_metric, oif, strict,
&do_rr);
--
2.14.2.920.gcf0c67979c-goog
