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Florian Westphal authored
The lockless workqueue garbage collector can race with packet path garbage collector to delete list nodes, as it calls tree_nodes_free() with the addresses of nodes that might have been free'd already from another cpu. To fix this, split gc into two phases. One phase to perform gc on the connections: From a locking perspective, this is the same as count_tree(): we hold rcu lock, but we do not change the tree, we only change the nodes' contents. The second phase acquires the tree lock and reaps empty nodes. This avoids a race condition of the garbage collection vs. packet path: If a node has been free'd already, the second phase won't find it anymore. This second phase is, from locking perspective, same as insert_tree(). The former only modifies nodes (list content, count), latter modifies the tree itself (rb_erase or rb_insert). Fixes: 5c789e13 ("netfilter: nf_conncount: Add list lock and gc worker, and RCU for init tree search") Reviewed-by:
Shawn Bohrer <sbohrer@cloudflare.com> Signed-off-by:
Florian Westphal <fw@strlen.de> Signed-off-by:
Pablo Neira Ayuso <pablo@netfilter.org>
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