virtio_net_hdr_tnl_to_skb() does not check that a UDP tunnel GSO
packet really has an outer IPv4/IPv6 header matching the declared
tunnel type. A guest, or any tap writer, can send a frame with another
outer ethertype (NSH in the report), and the GSO stack then builds
segments with skb->data before skb->head. The host crashes in
skb_under_panic() as soon as a header is pushed.
Patch 1 adds the missing check. Ethernet frames can carry VLAN tags
before the outer IP header; for IFF_TUN, skb->protocol is provided
by the caller.
Patch 2 fixes a selftest helper computing UDP checksums over a length
in network byte order.
Patch 3 adds tun selftests: valid outer IPv4 frames (plain and VLAN
tagged) are accepted, mismatched or non-IP outer headers are rejected.
Eric Dumazet (3):
net: virtio: validate outer protocol of UDP tunnel GSO packets
selftests: net: tuntap: fix UDP checksum length in
build_udp_packet_csum()
selftests: net: tun: test outer protocol of UDP tunnel GSO packets
include/linux/virtio_net.h | 28 ++++
tools/testing/selftests/net/tun.c | 130 +++++++++++++++++++
tools/testing/selftests/net/tuntap_helpers.h | 2 +-
3 files changed, 159 insertions(+), 1 deletion(-)
base-commit: 647b81ddefc6364290e67bf33c89d54971f8995e
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2.53.0