Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: tcp: call sk_data_ready() after listener migration When inet_csk_listen_stop() migrates an established child socket from a closing listener to another socket in the same SO_REUSEPORT group, the target listener gets a new accept-queue entry via inet_csk_reqsk_queue_add(), but that path never notifies the target listener's waiters. A nonblocking accept() still works because it checks the queue directly, but poll()/epoll_wait() waiters and blocking accept() callers can also remain asleep indefinitely. Call READ_ONCE(nsk->sk_data_ready)(nsk) after a successful migration in inet_csk_listen_stop(). However, after inet_csk_reqsk_queue_add() succeeds, the ref acquired in reuseport_migrate_sock() is effectively transferred to nreq->rsk_listener. Another CPU can then dequeue nreq via accept() or listener shutdown, hit reqsk_put(), and drop that listener ref. Since listeners are SOCK_RCU_FREE, wrap the post-queue_add() dereferences of nsk in rcu_read_lock()/rcu_read_unlock(), which also covers the existing sock_net(nsk) access in that path. The reqsk_timer_handler() path does not need the same changes for two reasons: half-open requests become readable only after the final ACK, where tcp_child_process() already wakes the listener; and once nreq is visible via inet_ehash_insert(), the success path no longer touches nsk directly.

Affected versions

Linux: 54b92e84193749c9968aff2dd46e3b0f42643e18 through before 7aa7933a5607b1e5b56f322d17265c1d0ea02c51 (git); 54b92e84193749c9968aff2dd46e3b0f42643e18 through before 14e9bb6eba8f59dcc637702e4744ae5e30660d76 (git); 54b92e84193749c9968aff2dd46e3b0f42643e18 through before ab5fdcd535645f6dbe6e9e21d96a08d141e88b4b (git); 54b92e84193749c9968aff2dd46e3b0f42643e18 through before bebd058ef40c67a81fe6d9ee8beaa4ede90e0704 (git); 54b92e84193749c9968aff2dd46e3b0f42643e18 through before 83bb57635d7cbafde32f865b577ecfd969f02337 (git); 54b92e84193749c9968aff2dd46e3b0f42643e18 through before 12625b4da84caf4d84a04988710a7b9bcf702b18 (git); 54b92e84193749c9968aff2dd46e3b0f42643e18 through before 3864c6ba1e041bc75342353a70fa2a2c6f909923 (git); 5.14; V3.1.6 through before * (custom) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.