[PATCH 6.6.y 0/2] CVE-2025-38264: backport fix series

[Artem Dinaburg]

Hi,

Please consider this backport series for CVE-2025-38264 to 6.6.y.

Apply the patches in this order:
1. llist: add interface to check if a node is on a list. (prerequisite)
2. nvme-tcp: sanitize request list handling (fix)

Patch 1 adds llist helpers to mark an unused node, test its membership,
and restore the unused state after dequeue.

Patch 2 initializes and resets NVMe/TCP request-list membership and
rejects R2T processing while the request remains queued. The code changes
in both patches are identical to upstream.

The complete fix is already present in 6.12.y, 6.18.y and 7.2.y.

Build-tested only as part of a cumulative 6.6.y series: x86_64 objects
(allmodconfig, CONFIG_WERROR=y); no runtime testing.

An LLM assisted with preparing these backports.

Thanks,
Artem Dinaburg