CVE-2026-90081 net/rds: use wq_has_sleeper() in rds_cong_map_updated()
A race condition in the Linux kernel RDS module can cause senders to block indefinitely, leading to a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90081?
CVE-2026-90081 is a vulnerability in Linux, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-90081?
How do I fix CVE-2026-90081?
Apply the vendor's patch.
Is CVE-2026-90081 being exploited?
There is no known exploitation of CVE-2026-90081 in the wild and no public exploit code.
Sources
Also known as AZL-102839, BELL-CVE-2026-90081, DEBIAN-CVE-2026-90081, GHSA-23r9-76mg-5gpp, UBUNTU-CVE-2026-90081.