[PATCH 3.16 15/55] openvswitch: fix panic with multiple vlan headers

From: Greg Kroah-Hartman
Date: Sun Oct 12 2014 - 22:28:07 EST

3.16-stable review patch. If anyone has any objections, please let me know.


From: Jiri Benc <jbenc@xxxxxxxxxx>

[ Upstream commit 2ba5af42a7b59ef01f9081234d8855140738defd ]

When there are multiple vlan headers present in a received frame, the first
one is put into vlan_tci and protocol is set to ETH_P_8021Q. Anything in the
skb beyond the VLAN TPID may be still non-linear, including the inner TCI
and ethertype. While ovs_flow_extract takes care of IP and IPv6 headers, it
does nothing with ETH_P_8021Q. Later, if OVS_ACTION_ATTR_POP_VLAN is
executed, __pop_vlan_tci pulls the next vlan header into vlan_tci.

This leads to two things:

1. Part of the resulting ethernet header is in the non-linear part of the
skb. When eth_type_trans is called later as the result of
OVS_ACTION_ATTR_OUTPUT, kernel BUGs in __skb_pull. Also, __pop_vlan_tci
is in fact accessing random data when it reads past the TPID.

2. network_header points into the ethernet header instead of behind it.
mac_len is set to a wrong value (10), too.

Reported-by: Yulong Pei <ypei@xxxxxxxxxx>
Signed-off-by: Jiri Benc <jbenc@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/openvswitch/actions.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -42,6 +42,9 @@ static int do_execute_actions(struct dat

static int make_writable(struct sk_buff *skb, int write_len)
+ if (!pskb_may_pull(skb, write_len))
+ return -ENOMEM;
if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
return 0;

@@ -70,6 +73,8 @@ static int __pop_vlan_tci(struct sk_buff

vlan_set_encap_proto(skb, vhdr);
skb->mac_header += VLAN_HLEN;
+ if (skb_network_offset(skb) < ETH_HLEN)
+ skb_set_network_header(skb, ETH_HLEN);

return 0;

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