net: sched: crash on blocks with goto chain action (a60b3f51) · Commits · 戴 / test

tcf_block_put_ext has assumed that all filters (and thus their goto actions) are destroyed in RCU callback and thus can not race with our list iteration. However, that is not true during netns cleanup (see tcf_exts_get_net comment). Prevent the user after free by holding all chains (except 0, that one is already held). foreach_safe is not enough in this case. To reproduce, run the following in a netns and then delete the ns: ip link add dtest type dummy tc qdisc add dev dtest ingress tc filter add dev dtest chain 1 parent ffff: handle 1 prio 1 flower action goto chain 2 Fixes: ("net_sched: remove tcf_block_put_deferred()") Signed-off-by:

Roman Kapl <code@rkapl.cz> Acked-by:

Jiri Pirko <jiri@mellanox.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/sched/cls_api.c

+12 −5

Original line number	Diff line number	Diff line
		@@ -336,7 +336,8 @@ static void tcf_block_put_final(struct work_struct *work)
		struct tcf_chain chain, tmp;

		rtnl_lock();
		/* Only chain 0 should be still here. */

		/* At this point, all the chains should have refcnt == 1. */
		list_for_each_entry_safe(chain, tmp, &block->chain_list, list)
		tcf_chain_put(chain);
		rtnl_unlock();
		@@ -344,15 +345,21 @@ static void tcf_block_put_final(struct work_struct *work)
		}

		/* XXX: Standalone actions are not allowed to jump to any chain, and bound
		* actions should be all removed after flushing. However, filters are now
		* destroyed in tc filter workqueue with RTNL lock, they can not race here.
		* actions should be all removed after flushing.
		*/
		void tcf_block_put_ext(struct tcf_block block, struct Qdisc q,
		struct tcf_block_ext_info *ei)
		{
		struct tcf_chain chain, tmp;
		struct tcf_chain *chain;

		list_for_each_entry_safe(chain, tmp, &block->chain_list, list)
		/* Hold a refcnt for all chains, except 0, so that they don't disappear
		* while we are iterating.
		*/
		list_for_each_entry(chain, &block->chain_list, list)
		if (chain->index)
		tcf_chain_hold(chain);

		list_for_each_entry(chain, &block->chain_list, list)
		tcf_chain_flush(chain);

		tcf_block_offload_unbind(block, q, ei);

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