Medium [CVE-2026-74566] make keyring key-chunk byte order agree with keyring_diff_objects

In the Linux kernel, the following vulnerability has been resolved: keys: make keyring key-chunk byte order agree with keyring_diff_objects() keyring_get_key_chunk() loads description bytes into the index chunk low address first, while keyring_diff_objects() numbers the first differing bit from the low end and folds the absolute byte index into the level without removing the inline-prefix offset the level already carries.

The two disagree on byte order and bit position, so the array can be told two keys first differ at a bit that does not differ in the chunk the walker uses, letting crafted descriptions collide into one node. This only changes the in-memory ordering used to place keys within a keyring; add, search and read of non-colliding keys are unaffected.

An inconsistency in how key descriptions are processed by the `keyring_get_key_chunk()` and `keyring_diff_objects()` functions could allow a local attacker to create specially crafted key descriptions. These crafted descriptions might collide, potentially leading to unexpected system behavior or a denial of service.

Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-1025.

Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 9. Will not fix / out of support: Red Hat Enterprise Linux 6.