CVE-2024-38558

In the Linux kernel, the following vulnerability has been resolved: net:
openvswitch: fix overwriting ct original tuple for ICMPv6
OVS_PACKET_CMD_EXECUTE has 3 main attributes: - OVS_PACKET_ATTR_KEY -
Packet metadata in a netlink format. - OVS_PACKET_ATTR_PACKET - Binary
packet content. - OVS_PACKET_ATTR_ACTIONS - Actions to execute on the
packet. OVS_PACKET_ATTR_KEY is parsed first to populate sw_flow_key
structure with the metadata like conntrack state, input port, recirculation
id, etc. Then the packet itself gets parsed to populate the rest of the
keys from the packet headers. Whenever the packet parsing code starts
parsing the ICMPv6 header, it first zeroes out fields in the key
corresponding to Neighbor Discovery information even if it is not an ND
packet. It is an ‘ipv6.nd’ field. However, the ‘ipv6’ is a union that
shares the space between ‘nd’ and ‘ct_orig’ that holds the original tuple
conntrack metadata parsed from the OVS_PACKET_ATTR_KEY. ND packets should
not normally have conntrack state, so it’s fine to share the space, but
normal ICMPv6 Echo packets or maybe other types of ICMPv6 can have the
state attached and it should not be overwritten. The issue results in all
but the last 4 bytes of the destination address being wiped from the
original conntrack tuple leading to incorrect packet matching and
potentially executing wrong actions in case this packet recirculates within
the datapath or goes back to userspace. ND fields should not be accessed in
non-ND packets, so not clearing them should be fine. Executing memset()
only for actual ND packets to avoid the issue. Initializing the whole thing
before parsing is needed because ND packet may not contain all the options.
The issue only affects the OVS_PACKET_CMD_EXECUTE path and doesn’t affect
packets entering OVS datapath from network interfaces, because in this case
CT metadata is populated from skb after the packet is already parsed.