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From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org
Subject: [PATCH 5/9] netfilter: nf_conncount: restart search when nodes have been erased
Date: Sat, 29 Dec 2018 13:57:59 +0100
Message-ID: <20181229125803.7415-6-pablo@netfilter.org> (raw)
In-Reply-To: <20181229125803.7415-1-pablo@netfilter.org>

From: Florian Westphal <fw@strlen.de>

Shawn Bohrer reported a following crash:
 |RIP: 0010:rb_erase+0xae/0x360
 [..]
 Call Trace:
  nf_conncount_destroy+0x59/0xc0 [nf_conncount]
  cleanup_match+0x45/0x70 [ip_tables]
  ...

Shawn tracked this down to bogus 'parent' pointer:
Problem is that when we insert a new node, then there is a chance that
the 'parent' that we found was also passed to tree_nodes_free() (because
that node was empty) for erase+free.

Instead of trying to be clever and detect when this happens, restart
the search if we have evicted one or more nodes.  To prevent frequent
restarts, do not perform gc on the second round.

Also, unconditionally schedule the gc worker.
The condition

  gc_count > ARRAY_SIZE(gc_nodes))

cannot be true unless tree grows very large, as the height of the tree
will be low even with hundreds of nodes present.

Fixes: 5c789e131cbb9 ("netfilter: nf_conncount: Add list lock and gc worker, and RCU for init tree search")
Reported-by: Shawn Bohrer <sbohrer@cloudflare.com>
Reviewed-by: Shawn Bohrer <sbohrer@cloudflare.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_conncount.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/net/netfilter/nf_conncount.c b/net/netfilter/nf_conncount.c
index 753132e4afa8..0a83c694a8f1 100644
--- a/net/netfilter/nf_conncount.c
+++ b/net/netfilter/nf_conncount.c
@@ -346,9 +346,10 @@ insert_tree(struct net *net,
 	struct nf_conncount_tuple *conn;
 	unsigned int count = 0, gc_count = 0;
 	bool node_found = false;
+	bool do_gc = true;
 
 	spin_lock_bh(&nf_conncount_locks[hash]);
-
+restart:
 	parent = NULL;
 	rbnode = &(root->rb_node);
 	while (*rbnode) {
@@ -381,21 +382,16 @@ insert_tree(struct net *net,
 		if (gc_count >= ARRAY_SIZE(gc_nodes))
 			continue;
 
-		if (nf_conncount_gc_list(net, &rbconn->list))
+		if (do_gc && nf_conncount_gc_list(net, &rbconn->list))
 			gc_nodes[gc_count++] = rbconn;
 	}
 
 	if (gc_count) {
 		tree_nodes_free(root, gc_nodes, gc_count);
-		/* tree_node_free before new allocation permits
-		 * allocator to re-use newly free'd object.
-		 *
-		 * This is a rare event; in most cases we will find
-		 * existing node to re-use. (or gc_count is 0).
-		 */
-
-		if (gc_count >= ARRAY_SIZE(gc_nodes))
-			schedule_gc_worker(data, hash);
+		schedule_gc_worker(data, hash);
+		gc_count = 0;
+		do_gc = false;
+		goto restart;
 	}
 
 	if (node_found)
-- 
2.11.0

  parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-29 12:57 [PATCH 0/9] Netfilter fixes for net Pablo Neira Ayuso
2018-12-29 12:57 ` [PATCH 1/9] netfilter: nf_tables: fix a missing check of nla_put_failure Pablo Neira Ayuso
2018-12-29 12:57 ` [PATCH 2/9] netfilter: nf_conncount: replace CONNCOUNT_LOCK_SLOTS with CONNCOUNT_SLOTS Pablo Neira Ayuso
2018-12-29 12:57 ` [PATCH 3/9] netfilter: nf_conncount: don't skip eviction when age is negative Pablo Neira Ayuso
2018-12-29 12:57 ` [PATCH 4/9] netfilter: nf_conncount: split gc in two phases Pablo Neira Ayuso
2018-12-29 12:57 ` Pablo Neira Ayuso [this message]
2018-12-29 12:58 ` [PATCH 6/9] netfilter: nf_conncount: merge lookup and add functions Pablo Neira Ayuso
2018-12-29 12:58 ` [PATCH 7/9] netfilter: nf_conncount: move all list iterations under spinlock Pablo Neira Ayuso
2018-12-29 12:58 ` [PATCH 8/9] netfilter: nf_conncount: speculative garbage collection on empty lists Pablo Neira Ayuso
2018-12-29 12:58 ` [PATCH 9/9] netfilter: nf_conncount: fix argument order to find_next_bit Pablo Neira Ayuso
2018-12-29 22:33 ` [PATCH 0/9] Netfilter fixes for net David Miller

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