bonding: limit BOND_MODE_8023AD to Ethernet devices
CVE: CVE-2026-23099
Component: kernel
CWE: CWE-20
Severity: Moderate
CVSS v3: 5.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Release date: 2026-02-04T00:00:00+00:00

In the Linux kernel, the following vulnerability has been resolved:

bonding: limit BOND_MODE_8023AD to Ethernet devices

BOND_MODE_8023AD makes sense for ARPHRD_ETHER only.

syzbot reported:

 BUG: KASAN: global-out-of-bounds in __hw_addr_create net/core/dev_addr_lists.c:63 [inline]
 BUG: KASAN: global-out-of-bounds in __hw_addr_add_ex+0x25d/0x760 net/core/dev_addr_lists.c:118
Read of size 16 at addr ffffffff8bf94040 by task syz.1.3580/19497

CPU: 1 UID: 0 PID: 19497 Comm: syz.1.3580 Tainted: G             L      syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
  dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
  print_address_description mm/kasan/report.c:378 [inline]
  print_report+0xca/0x240 mm/kasan/report.c:482
  kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
  kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200
  __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
  __hw_addr_create net/core/dev_addr_lists.c:63 [inline]
  __hw_addr_add_ex+0x25d/0x760 net/core/dev_addr_lists.c:118
  __dev_mc_add net/core/dev_addr_lists.c:868 [inline]
  dev_mc_add+0xa1/0x120 net/core/dev_addr_lists.c:886
  bond_enslave+0x2b8b/0x3ac0 drivers/net/bonding/bond_main.c:2180
  do_set_master+0x533/0x6d0 net/core/rtnetlink.c:2963
  do_setlink+0xcf0/0x41c0 net/core/rtnetlink.c:3165
  rtnl_changelink net/core/rtnetlink.c:3776 [inline]
  __rtnl_newlink net/core/rtnetlink.c:3935 [inline]
  rtnl_newlink+0x161c/0x1c90 net/core/rtnetlink.c:4072
  rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6958
  netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
  netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
  netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
  netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
  sock_sendmsg_nosec net/socket.c:727 [inline]
  __sock_sendmsg+0x21c/0x270 net/socket.c:742
  ____sys_sendmsg+0x505/0x820 net/socket.c:2592
  ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
  __sys_sendmsg+0x164/0x220 net/socket.c:2678
  do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
  __do_fast_syscall_32+0x1dc/0x560 arch/x86/entry/syscall_32.c:307
  do_fast_syscall_32+0x34/0x80 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
 </TASK>

The buggy address belongs to the variable:
 lacpdu_mcast_addr+0x0/0x40

Statement: A kernel out of bounds access can be triggered in the bonding driver when BOND_MODE_8023AD is used with a non Ethernet slave device type. The 8023AD path adds the LACP multicast address and the address list code assumes an Ethernet address length. With a mismatched device type this can cause a global out of bounds read or write involving lacpdu_mcast_addr as reported by KASAN. The likely outcome is a kernel crash which results in denial of service. For the CVSS the PR is H because creating and modifying bonding configuration requires CAP_NET_ADMIN in most environments. The issue is not network reachable and is triggered by local netlink configuration operations rather than packet traffic. Impact is primarily availability.

Remediation: