Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
ipv6: release nexthop on device removal
The CI is hitting some aperiodic hangup at device removal time in the pmtu.sh self-test:
unregister_netdevice: waiting for veth_A-R1 to become free. Usage count = 6 ref_tracker: veth_A-R1@ffff888013df15d8 has 1/5 users at dst_init+0x84/0x4a0 dst_alloc+0x97/0x150 ip6_dst_alloc+0x23/0x90 ip6_rt_pcpu_alloc+0x1e6/0x520 ip6_pol_route+0x56f/0x840 fib6_rule_lookup+0x334/0x630 ip6_route_output_flags+0x259/0x480 ip6_dst_lookup_tail.constprop.0+0x5c2/0x940 ip6_dst_lookup_flow+0x88/0x190 udp_tunnel6_dst_lookup+0x2a7/0x4c0 vxlan_xmit_one+0xbde/0x4a50 [vxlan] vxlan_xmit+0x9ad/0xf20 [vxlan] dev_hard_start_xmit+0x10e/0x360 __dev_queue_xmit+0xf95/0x18c0 arp_solicit+0x4a2/0xe00 neigh_probe+0xaa/0xf0
While the first suspect is the dst_cache, explicitly tracking the dst owing the last device reference via probes proved such dst is held by the nexthop in the originating fib6_info.
Similar to commit f5b51fe804ec (“ipv6: route: purge exception on removal”), we need to explicitly release the originating fib info when disconnecting a to-be-removed device from a live ipv6 dst: move the fib6_info cleanup into ip6_dst_ifdown().
Tested running:
./pmtu.sh cleanup_ipv6_exception
in a tight loop for more than 400 iterations with no spat, running an unpatched kernel I observed a splat every ~10 iterations.
Details
- Affected product:
- AlmaLinux 9.2 ESU , Amazon Linux 2 ELS , Oracle Linux 7 ELS , TuxCare 9.6 ESU , Ubuntu 20.04 ELS
- Affected packages:
- kernel @ 5.14.0-11 (+5 more)
Fixes
KernelCare state
Live-patch status from KernelCare for each operating system.
| Operating system | Status | Covered kernels |
|---|---|---|
| Amazon Linux 2023 | Planned | — |
| Debian 12 | Planned | — |
| Oracle Linux 8 UEK 7 | In Progress | — |
| Oracle Linux 9 UEK 7 | In Progress | — |
| Proxmox VE 7 5.15 | Released |
47 kernels
|
| Ubuntu 20.04 HWE AWS | Released |
57 kernels
|
| Ubuntu 20.04 HWE Azure | Released |
40 kernels
|
| Ubuntu 22.04 | Released |
77 kernels
|
| Ubuntu 22.04 AWS | Released |
68 kernels
|
| Ubuntu 22.04 Azure | Released |
64 kernels
|
| Ubuntu 24.04 | Released |
20 kernels
|
| Ubuntu 24.04 AWS | Ready For Release | — |