net/rds: use wq_has_sleeper() in rds_cong_map_updated()

Summary

In the Linux kernel, the following vulnerability has been resolved: net/rds: use wq_has_sleeper() in rds_cong_map_updated() rds_cong_map_updated() runs after a peer's congestion map has been rewritten (by rds_tcp_cong_recv() and rds_ib_cong_recv(), or the clear-all in the loopback and IB send-completion paths). It bumps rds_cong_generation and then checks waitqueue_active() on map->m_waitq and on rds_poll_waitq to decide whether anyone needs waking. atomic_inc() carries no ordering and waitqueue_active() is a plain load, so nothing orders the map and generation stores before the wait queue reads. The waiters do the mirror image: rds_cong_wait() adds itself to m_waitq and then tests the port bit, and rds_poll() registers on rds_poll_waitq and then reads the generation. That is the store-buffering pattern described above waitqueue_active() in include/linux/wait.h - the updater can observe an empty wait queue while the waiter still observes the port as congested, and no wake-up is issued. rds_cong_wait() is an interruptible sleep with no timeout, so a sender blocked on a congested port stays blocked until the next congestion update from that peer arrives or a signal is delivered. A poll() waiter misses the map-updated notification the same way. Use wq_has_sleeper(), which is waitqueue_active() preceded by the required full barrier, as rds_tcp_state_change() already does for the same pattern.

Timeline

1. Sep 17, 2026, 4:05 PM UTCCVE published
2. Oct 19, 2026, 8:57 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in 2a809d7896dbf18e1ecfbdd930f71c9fc298b16d; From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in fa4b98e891fda28cc0638d809c6125ec63d8319d; From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in 0e169f6a2adeb17b5577ed7e8abd642465bb50ec; From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in 42884bd8b8fd023d6a610a695bd5ddd1d5dece17; From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in a526214b9f0548ca0e53a6e0d1727d8ea9befc23; From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in bf2b8130723efcb5b86c3ddb6317c3a9b2a9cfc5; From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in 281f9fda2e06d6c211bb365a5379ed2e05cc2e21; From 922cb17a5c812fcc9ebee249f4109db099896941 · fixed in d4f484661961636eb90d287050959e613795f73a

• Linux Linux

  2.6.30

• KernelLinux

  From 2.6.30 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 8