CVE-2024-56751

ipv6: release nexthop on device removal

State: Published
Severity: Not scored
Published: Dec 29, 2024
Updated: May 11, 2026
Reserved: Dec 29, 2024

Description

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.

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before 77aa9855a878fb43f547ddfbda3127a1e88ad31aAffected f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before b2f26a27ea3f72f75d18330f76f5d1007c791848Affected f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before 43e25adc80269f917d2a195f0d59f74cdd182955Affected f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before a3c3f8a4d025acc8c857246ec2b812c59102487aAffected f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before 0e4c6faaef8a24b762a24ffb767280e263ef8e10Affected f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before eb02688c5c45c3e7af7e71f036a7144f5639cbfeAffected
LinuxLinux	5.3Affected before 5.3Not affected 5.15.181 through 5.15.Not affected 6.1.120 through 6.1.Not affected 6.6.64 through 6.6.Not affected 6.11.11 through 6.11.Not affected 6.12.2 through 6.12.*Not affected 6.13 and laterNot affected

Product

Versions

LinuxLinux

f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before 77aa9855a878fb43f547ddfbda3127a1e88ad31aAffected
f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before b2f26a27ea3f72f75d18330f76f5d1007c791848Affected
f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before 43e25adc80269f917d2a195f0d59f74cdd182955Affected
f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before a3c3f8a4d025acc8c857246ec2b812c59102487aAffected
f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before 0e4c6faaef8a24b762a24ffb767280e263ef8e10Affected
f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 to before eb02688c5c45c3e7af7e71f036a7144f5639cbfeAffected

LinuxLinux

5.3Affected
before 5.3Not affected
5.15.181 through 5.15.*Not affected
6.1.120 through 6.1.*Not affected
6.6.64 through 6.6.*Not affected
6.11.11 through 6.11.*Not affected
6.12.2 through 6.12.*Not affected
6.13 and laterNot affected

References

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