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

Official 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 packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/6f552364d97cf4005c7a58f11c9f79e14e269865
• https://git.kernel.org/stable/c/a94b1dfc82454c5bc068e71c25393af674daf63b
• https://git.kernel.org/stable/c/5a806ed1eb46850ca4159a18b2a8c4b70f0c1341
• https://git.kernel.org/stable/c/3d401934b7edb3ccb07d982dabadd04c45ee307c
• https://git.kernel.org/stable/c/ed7ee0cd0e136d02f87f13181b1a89880463c7e9
• https://git.kernel.org/stable/c/a269795107f45adc95975a83324f8fef40bec4ce
• https://git.kernel.org/stable/c/3764627b30a283e611e652c4a2bb8cdc74a75a99
• https://git.kernel.org/stable/c/6d0c8b7073913011459cf968cbbadd341e166bc3