[PATCH 6.6.y 0/2] CVE-2025-71272, CVE-2026-43317: backport fix series

[Artem Dinaburg]

Hi,

Please consider this backport series for CVE-2025-71272, CVE-2026-43317 to
6.6.y.

Apply the patches in this order:
1. most: core: fix resource leak in most_register_interface error paths (fix)
2. most: core: fix leak on early registration failure (fix)

Patch 1 initializes the interface device before ID allocation and releases
the device, ID and private storage on registration failures.

Patch 2 moves callback and channel-count validation after device
initialization so those early failures also release the device. 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