Vulnerability record · CVE-2026-64281 · published 25 July 2026
CVE-2026-64281: Linux kernel vulnerability
Linux · Linux Kernel
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 ]
Description
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 ]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
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Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2026-64281), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.
