CVE-2026-64281

In the Linux kernel, the following vulnerability has been resolved:

svcrdma: wake sq waiters when the transport closes

Threads parked in svc_rdma_sq_wait() on sc_sq_ticket_wait or

sc_send_wait can hang indefinitely in TASK_UNINTERRUPTIBLE state

across transport teardown, pinning svc_xprt references and

blocking svc_rdma_free().

The close path sets XPT_CLOSE before invoking xpo_detach and both

wait_event predicates include an XPT_CLOSE term, but the

predicates are re-evaluated only on wakeup. sc_sq_ticket_wait has

no completion-driven wake path; it is advanced solely by the

chained ticket handoff inside svc_rdma_sq_wait() itself. Without

an explicit wake at close, parked threads never observe

XPT_CLOSE, hold their svc_xprt_get reference forever, and

svc_rdma_free() blocks on xpt_ref dropping to zero.

Two close entry points reach this transport. Local teardown runs

svc_rdma_detach() from svc_handle_xprt() -> svc_delete_xprt() ->

xpo_detach() on a worker thread. A remote disconnect arrives at

svc_rdma_cma_handler(), which calls svc_xprt_deferred_close():

that sets XPT_CLOSE and enqueues the transport but does not

access either RDMA waitqueue, so a worker already parked in

svc_rdma_sq_wait() never re-evaluates its predicate. With every

worker parked on this transport, no thread is available to run

the local teardown either, and the wake site there is

unreachable.

Introduce svc_rdma_xprt_deferred_close(), a thin svcrdma wrapper

that calls svc_xprt_deferred_close() and then wakes both

sc_sq_ticket_wait and sc_send_wait. Convert the svcrdma producers

that called svc_xprt_deferred_close() directly:

svc_rdma_cma_handler(), qp_event_handler(),

svc_rdma_post_send_err(), svc_rdma_wc_send(), the sendto drop

path, the rw completion error paths, and the recvfrom flush and

read-list error paths.

Wake both waitqueues from svc_rdma_detach() as well. The

synchronous svc_xprt_close() path (backchannel ENOTCONN, device

removal via svc_rdma_xprt_done) reaches detach without flowing

through svc_xprt_deferred_close() and therefore does not invoke

the new helper.

[ cel: add svc_rdma_xprt_deferred_close() to complete the fix ]