CVE-2026-98072: net/rds: use wq_has_sleeper() in release_in_xmit()

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-25 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: net/rds: use wq_has_sleeper() in release_in_xmit() release_in_xmit() clears RDS_IN_XMIT with clear_bit_unlock() and then checks waitqueue_active() to decide whether anyone needs waking. clear_bit_unlock() is only a release operation: it orders the critical section before the bit clear, but does not order the subsequent plain load of the wait queue head after it. The waiter side does the mirror image - it adds itself to the wait queue and then tests the bit. That is the classic store-buffering pattern: the releasing CPU can read the wait queue as empty while the waiting CPU still reads the bit as set, so the sleeper is never woken. The waiters are rds_conn_shutdown() and rds_tcp_reset_callbacks(), both in uninterruptible wait_event() with no timeout. A lost wake-up strands the shutdown worker on its single-threaded workqueue until some other sender releases the bit again - and on a connection that is being torn down precisely because it failed, there may never be another sender. The barrier used to be there: release_in_xmit() did clear_bit() followed by smp_mb__after_atomic() until commit 1422f28826d2 ("rds: introduce acquire/release ordering in acquire/release_in_xmit()") folded both into clear_bit_unlock(), which strengthened the lock hand-off but silently dropped the full barrier the wake-up check depends on. The refill counterpart, release_refill() in net/rds/ib_recv.c, still carries its smp_mb__after_atomic() for exactly this reason. Use wq_has_sleeper(), which is waitqueue_active() preceded by the required full barrier.

Affected products

Linux kernel: from 5.10.214 before 5.10.271; from 5.15.153 before 5.15.222; from 6.1.83 before 6.1.189; from 6.6.23 before 6.6.158; from 4.19.311 before 4.20; from 5.4.273 before 5.5 — fixed in 4.20, 5.10.271, 5.15.222, 5.5, 6.1.189, 6.6.158

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.10.271, 5.15.222, 5.5. Check the vendor advisory for mitigations.

References

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