4.19-stable review patch. If anyone has any objections, please let me know.
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From: Florian Westphal fw@strlen.de
commit f7fcc98dfc2d136722007fec0debbed761679b94 upstream.
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: 5c789e131cbb9 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/netfilter/nf_conncount.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-)
--- a/net/netfilter/nf_conncount.c +++ b/net/netfilter/nf_conncount.c @@ -500,16 +500,32 @@ static void tree_gc_worker(struct work_s for (node = rb_first(root); node != NULL; node = rb_next(node)) { rbconn = rb_entry(node, struct nf_conncount_rb, node); if (nf_conncount_gc_list(data->net, &rbconn->list)) - gc_nodes[gc_count++] = rbconn; + gc_count++; } rcu_read_unlock();
spin_lock_bh(&nf_conncount_locks[tree]); + if (gc_count < ARRAY_SIZE(gc_nodes)) + goto next; /* do not bother */
- if (gc_count) { - tree_nodes_free(root, gc_nodes, gc_count); + gc_count = 0; + node = rb_first(root); + while (node != NULL) { + rbconn = rb_entry(node, struct nf_conncount_rb, node); + node = rb_next(node); + + if (rbconn->list.count > 0) + continue; + + gc_nodes[gc_count++] = rbconn; + if (gc_count >= ARRAY_SIZE(gc_nodes)) { + tree_nodes_free(root, gc_nodes, gc_count); + gc_count = 0; + } }
+ tree_nodes_free(root, gc_nodes, gc_count); +next: clear_bit(tree, data->pending_trees);
next_tree = (tree + 1) % CONNCOUNT_SLOTS;