CVE-2026-68338net/packet: avoid fanout hook re-registration after unregister

Official description

In the Linux kernel, the following vulnerability has been resolved: net/packet: avoid fanout hook re-registration after unregister packet_set_ring() temporarily detaches a socket from packet delivery while reconfiguring its ring. It records the previous running state, clears po->num, unregisters the protocol hook when needed, drops po->bind_lock, and later restores po->num and re-registers the hook from the saved was_running value. That unlocked window can race with NETDEV_UNREGISTER. The notifier can observe the socket as not running, skip __unregister_prot_hook(), and invalidate the per-socket binding by setting po->ifindex to -1 and clearing po->prot_hook.dev. A one-member fanout group can still retain its shared fanout hook device pointer. When packet_set_ring() resumes, re-registering solely from the stale was_running state can re-add the fanout hook after the device has been unregistered. Treat po->ifindex == -1 as an invalidated binding after reacquiring po->bind_lock. This is distinct from ifindex 0, the normal unbound/wildcard state: ifindex -1 marks an existing device binding that was invalidated when the device was unregistered. Restore po->num as before, but do not re-register the hook if device unregister already detached the socket.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/acb40ebfa5c4d62f84339fcbf713f2a9fd033a71
• https://git.kernel.org/stable/c/c820f4b7f2fa38f8769db0d0cefdd94e2721504d
• https://git.kernel.org/stable/c/4628efbdc7affd094181f5263e65c1062e31f15f
• https://git.kernel.org/stable/c/80ec024d53a05c60ad1d08968dcf745f10c1665c
• https://git.kernel.org/stable/c/0a052e0808e015e68144a9877e6ef42b952c49fa
• https://git.kernel.org/stable/c/1bc55c29cd85818e9052f17deb287d5a11fb817f
• https://git.kernel.org/stable/c/a885387dae7986a55bae5c77a15bdd447f64e9b9
• https://git.kernel.org/stable/c/50aff80475abd3533eef4320477037e6fcc6b56e