Description
In the Linux kernel, the following vulnerability has been resolved:vxlan: Fix NPD in {arp,neigh}_reduce() when using nexthop objectsWhen the "proxy" option is enabled on a VXLAN device, the device willsuppress ARP requests and IPv6 Neighbor Solicitation messages if it isable to reply on behalf of the remote host. That is, if a matching andvalid neighbor entry is configured on the VXLAN device whose MAC addressis not behind the "any" remote (0.0.0.0 / ::).The code currently assumes that the FDB entry for the neighbor's MACaddress points to a valid remote destination, but this is incorrect ifthe entry is associated with an FDB nexthop group. This can result in aNPD [1][3] which can be reproduced using [2][4].Fix by checking that the remote destination exists before dereferencingit.[1]BUG: kernel NULL pointer dereference, address: 0000000000000000[...]CPU: 4 UID: 0 PID: 365 Comm: arping Not tainted 6.17.0-rc2-virtme-g2a89cb21162c #2 PREEMPT(voluntary)Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014RIP: 0010:vxlan_xmit+0xb58/0x15f0[...]Call Trace: dev_hard_start_xmit+0x5d/0x1c0 __dev_queue_xmit+0x246/0xfd0 packet_sendmsg+0x113a/0x1850 __sock_sendmsg+0x38/0x70 __sys_sendto+0x126/0x180 __x64_sys_sendto+0x24/0x30 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x4b/0x53[2] #!/bin/bash ip address add 192.0.2.1/32 dev lo ip nexthop add id 1 via 192.0.2.2 fdb ip nexthop add id 10 group 1 fdb ip link add name vx0 up type vxlan id 10010 local 192.0.2.1 dstport 4789 proxy ip neigh add 192.0.2.3 lladdr 00:11:22:33:44:55 nud perm dev vx0 bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10 arping -b -c 1 -s 192.0.2.1 -I vx0 192.0.2.3[3]BUG: kernel NULL pointer dereference, address: 0000000000000000[...]CPU: 13 UID: 0 PID: 372 Comm: ndisc6 Not tainted 6.17.0-rc2-virtmne-g6ee90cb26014 #3 PREEMPT(voluntary)Hardware name: QEMU Standard PC (i440FX + PIIX, 1v996), BIOS 1.17.0-4.fc41 04/01/2x014RIP: 0010:vxlan_xmit+0x803/0x1600[...]Call Trace: dev_hard_start_xmit+0x5d/0x1c0 __dev_queue_xmit+0x246/0xfd0 ip6_finish_output2+0x210/0x6c0 ip6_finish_output+0x1af/0x2b0 ip6_mr_output+0x92/0x3e0 ip6_send_skb+0x30/0x90 rawv6_sendmsg+0xe6e/0x12e0 __sock_sendmsg+0x38/0x70 __sys_sendto+0x126/0x180 __x64_sys_sendto+0x24/0x30 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x4b/0x53RIP: 0033:0x7f383422ec77[4] #!/bin/bash ip address add 2001:db8:1::1/128 dev lo ip nexthop add id 1 via 2001:db8:1::1 fdb ip nexthop add id 10 group 1 fdb ip link add name vx0 up type vxlan id 10010 local 2001:db8:1::1 dstport 4789 proxy ip neigh add 2001:db8:1::3 lladdr 00:11:22:33:44:55 nud perm dev vx0 bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10 ndisc6 -r 1 -s 2001:db8:1::1 -w 1 2001:db8:1::3 vx0
POC
Reference
No PoCs from references.
Github
- https://github.com/w4zu/Debian_security
