From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org
Subject: [PATCH 3/4] netfilter: sync with packet rx also after removing queue entries
Date: Mon, 19 Oct 2015 20:22:54 +0200 [thread overview]
Message-ID: <1445278975-2412-4-git-send-email-pablo@netfilter.org> (raw)
In-Reply-To: <1445278975-2412-1-git-send-email-pablo@netfilter.org>
From: Florian Westphal <fw@strlen.de>
We need to sync packet rx again after flushing the queue entries.
Otherwise, the following race could happen:
cpu1: nf_unregister_hook(H) called, H unliked from lists, calls
synchronize_net() to wait for packet rx completion.
Problem is that while no new nf_queue_entry structs that use H can be
allocated, another CPU might receive a verdict from userspace just before
cpu1 calls nf_queue_nf_hook_drop to remove this entry:
cpu2: receive verdict from userspace, lock queue
cpu2: unlink nf_queue_entry struct E, which references H, from queue list
cpu1: calls nf_queue_nf_hook_drop, blocks on queue spinlock
cpu2: unlock queue
cpu1: nf_queue_nf_hook_drop drops affected queue entries
cpu2: call nf_reinject for E
cpu1: kfree(H)
cpu2: potential use-after-free for H
Cc: Eric W. Biederman <ebiederm@xmission.com>
Fixes: 085db2c04557 ("netfilter: Per network namespace netfilter hooks.")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 8e47f81..21a0856 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -152,6 +152,8 @@ void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg)
#endif
synchronize_net();
nf_queue_nf_hook_drop(net, &entry->ops);
+ /* other cpu might still process nfqueue verdict that used reg */
+ synchronize_net();
kfree(entry);
}
EXPORT_SYMBOL(nf_unregister_net_hook);
--
2.1.4
next prev parent reply other threads:[~2015-10-19 18:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-19 18:22 [PATCH 0/4] Netfilter fixes for net Pablo Neira Ayuso
2015-10-19 18:22 ` [PATCH 1/4] netfilter: fix Kconfig dependencies for nf_dup_ipv{4,6} Pablo Neira Ayuso
2015-10-19 18:22 ` [PATCH 2/4] netfilter: ipt_rpfilter: remove the nh_scope test in rpfilter_lookup_reverse Pablo Neira Ayuso
2015-10-19 18:22 ` Pablo Neira Ayuso [this message]
2015-10-19 18:22 ` [PATCH 4/4] netfilter: ipset: Fix sleeping memory allocation in atomic context Pablo Neira Ayuso
2015-10-22 2:27 ` [PATCH 0/4] Netfilter fixes for net David Miller
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