When executing IPv6 address rewrite actions on IPv6 fragments, set_ipv6_addr() might attempt to recalculate the L4 header checksum calling skb_transport_header() with an uninitialized transport header. This can potentially lead to a OOB write. A warning is triggered with DEBUG_NET=y.
Fix this by recalculating the checksum only if there is a valid transport header in the skb. Otherwise, assume this is a fragment and skip it. See the syzbot trace: !skb_transport_header_was_set(skb) WARNING: ./include/linux/skbuff.h:3075 at skb_transport_header include/linux/skbuff.h:3075 [inline], CPU#1: syz-executor463/5635 WARNING: ./include/linux/skbuff.h:3075 at skb_transport_offset include/linux/skbuff.h:3250 [inline], CPU#1: syz-executor463/5635 WARNING: ./include/linux/skbuff.h:3075 at update_ipv6_checksum net/openvswitch/actions.c:361 [inline], CPU#1: syz-executor463/5635 WARNING: ./include/linux/skbuff.h:3075 at set_ipv6_addr+0x462/0x660 net/openvswitch/actions.c:399, CPU#1: syz-executor463/5635 [...] RIP: 0010:skb_transport_header include/linux/skbuff.h:3075 [inline] RIP: 0010:skb_transport_offset include/linux/skbuff.h:3250 [inline] RIP: 0010:update_ipv6_checksum net/openvswitch/actions.c:361 [inline] RIP: 0010:set_ipv6_addr+0x462/0x660 net/openvswitch/actions.c:399 [...] Call Trace: <TASK> set_ipv6 net/openvswitch/actions.c:531 [inline] do_execute_actions+0x557e/0x8600 net/openvswitch/actions.c:1366 ovs_execute_actions+0xde/0x520 net/openvswitch/actions.c:1592 ovs_packet_cmd_execute+0xb4f/0xf10 net/openvswitch/datapath.c:705 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2572 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1361 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1916 sock_sendmsg_nosec+0x14e/0x190 net/socket.c:800 Reported-by: [email protected] Closes: https://syzkaller.appspot.com/bug?extid=4cc63fcfb3845e149969 Fixes: 3fdbd1ce11e5 ("openvswitch: add ipv6 'set' action") Signed-off-by: Fernando Fernandez Mancera <[email protected]> --- net/openvswitch/actions.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c index dc5ff859f114..a14668565ec4 100644 --- a/net/openvswitch/actions.c +++ b/net/openvswitch/actions.c @@ -395,7 +395,7 @@ static void set_ipv6_addr(struct sk_buff *skb, u8 l4_proto, __be32 addr[4], const __be32 new_addr[4], bool recalculate_csum) { - if (recalculate_csum) + if (recalculate_csum && skb_transport_header_was_set(skb)) update_ipv6_checksum(skb, l4_proto, addr, new_addr); skb_clear_hash(skb); -- 2.55.0 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
