[NETFILTER]: bridge-netfilter: fix net_device refcnt leaks (2dc2f207) · Commits · 戴 / test

When packets are flood-forwarded to multiple output devices, the bridge-netfilter code reuses skb->nf_bridge for each clone to store the bridge port. When queueing packets using NFQUEUE netfilter takes a reference to skb->nf_bridge->physoutdev, which is overwritten when the packet is forwarded to the second port. This causes refcount unterflows for the first device and refcount leaks for all others. Additionally this provides incorrect data to the iptables physdev match. Unshare skb->nf_bridge by copying it if it is shared before assigning the physoutdev device. Reported, tested and based on initial patch by Jan Christoph Nordholz <hesso@pool.math.tu-berlin.de>. Signed-off-by:

Patrick McHardy <kaber@trash.net> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/bridge/br_netfilter.c

+27 −0

Original line number	Diff line number	Diff line
		@@ -142,6 +142,23 @@ static inline struct nf_bridge_info nf_bridge_alloc(struct sk_buff skb)
		return skb->nf_bridge;
		}

		static inline struct nf_bridge_info nf_bridge_unshare(struct sk_buff skb)
		{
		struct nf_bridge_info *nf_bridge = skb->nf_bridge;

		if (atomic_read(&nf_bridge->use) > 1) {
		struct nf_bridge_info *tmp = nf_bridge_alloc(skb);

		if (tmp) {
		memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
		atomic_set(&tmp->use, 1);
		nf_bridge_put(nf_bridge);
		}
		nf_bridge = tmp;
		}
		return nf_bridge;
		}

		static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
		{
		unsigned int len = nf_bridge_encap_header_len(skb);
		@@ -637,6 +654,11 @@ static unsigned int br_nf_forward_ip(unsigned int hook, struct sk_buff *skb,
		if (!skb->nf_bridge)
		return NF_ACCEPT;

		/* Need exclusive nf_bridge_info since we might have multiple
		* different physoutdevs. */
		if (!nf_bridge_unshare(skb))
		return NF_DROP;

		parent = bridge_parent(out);
		if (!parent)
		return NF_DROP;
		@@ -718,6 +740,11 @@ static unsigned int br_nf_local_out(unsigned int hook, struct sk_buff *skb,
		if (!skb->nf_bridge)
		return NF_ACCEPT;

		/* Need exclusive nf_bridge_info since we might have multiple
		* different physoutdevs. */
		if (!nf_bridge_unshare(skb))
		return NF_DROP;

		nf_bridge = skb->nf_bridge;
		if (!(nf_bridge->mask & BRNF_BRIDGED_DNAT))
		return NF_ACCEPT;

Admin message