Commit 17ecf590 authored Oct 06, 2017 by Wei Wang Committed by David S. Miller Oct 07, 2017

ipv6: add key length check into rt6_select()



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 <weiwan@google.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8d1040e8

net/ipv6/route.c

+14 −0

Original line number	Diff line number	Diff line
		@@ -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);

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