CVE-2026-23169: Concurrent Execution using Shared Resource with Improper Synchronization

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

mptcp: fix race in mptcp_pm_nl_flush_addrs_doit()

syzbot and Eulgyu Kim reported crashes in mptcp_pm_nl_get_local_id() and/or mptcp_pm_nl_is_backup()

Root cause is list_splice_init() in mptcp_pm_nl_flush_addrs_doit() which is not RCU ready.

list_splice_init_rcu() can not be called here while holding pernet->lock spinlock.

Many thanks to Eulgyu Kim for providing a repro and testing our patches.