net/packet: fix overflow in tpacket_rcv

Using tp_reserve to calculate netoff can overflow as
tp_reserve is unsigned int and netoff is unsigned short.

This may lead to macoff receving a smaller value then
sizeof(struct virtio_net_hdr), and if po->has_vnet_hdr
is set, an out-of-bounds write will occur when
calling virtio_net_hdr_from_skb.

The bug is fixed by converting netoff to unsigned int
and checking if it exceeds USHRT_MAX.

This addresses CVE-2020-14386

Fixes: 8913336a7e8d ("packet: add PACKET_RESERVE sockopt")
Signed-off-by: Or Cohen <>
Signed-off-by: Eric Dumazet <>
(backported from
Signed-off-by: Robert Kolchmeyer <>

TEST=Manually tried the reproducer before and after this fix.
RELEASE_NOTE=Fixed overflow in tpacket_rcv, which caused CVE-2020-14386.

Change-Id: Ifc451bdd97c124917e49023db2d7f3a0356d4801
Tested-by: Robert Kolchmeyer <>
Reviewed-by: Roy Yang <>
(cherry picked from commit c46f8a87c479cd2e964513992d3eab92eff5c160)
1 file changed