When a packet arrives on an ARPHRD_NONE device (e.g. TUN), ovs_flow_key_extract() trusts the user-provided skb->protocol field: if it is ETH_P_TEB, the packet is classified as MAC_PROTO_ETHERNET and key_extract() is called without ensuring the skb has ETH_HLEN (14) bytes of linear data. key_extract() unconditionally pulls 2 * ETH_ALEN bytes for MAC addresses and parse_ethertype() pulls 2 more, either of which triggers a kernel BUG in __skb_pull() when the linear area is too small. kernel BUG at include/linux/skbuff.h:2848! RIP: 0010:key_extract+0xa7e/0xd90 net/openvswitch/flow.c:933 ovs_flow_key_extract+0x419/0xa70 ovs_vport_receive+0x222/0x390 netdev_frame_hook+0x3e0/0x630 tun_get_user+0x2d0c/0x38e0 Fixed by adding check_header(skb, ETH_HLEN) in ovs_flow_key_extract() before calling key_extract(). Fixes: 217ac77a3c25 ("openvswitch: allow L3 netdev ports") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Cen Zhang (Microsoft) --- net/openvswitch/flow.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c index 66366982f604..a0f9d788d284 100644 --- a/net/openvswitch/flow.c +++ b/net/openvswitch/flow.c @@ -1035,6 +1035,13 @@ int ovs_flow_key_extract(const struct ip_tunnel_info *tun_info, return res; key->mac_proto = res; + if (res == MAC_PROTO_ETHERNET) { + int err = check_header(skb, ETH_HLEN); + + if (unlikely(err)) + return err; + } + #if IS_ENABLED(CONFIG_NET_TC_SKB_EXT) if (tc_skb_ext_tc_enabled()) { tc_ext = skb_ext_find(skb, TC_SKB_EXT); -- 2.53.0