dm-thin: fix metadata refcount underflow

These records connect through source-stated identifiers. Shared identifiers or dates alone do not establish shared exposure, root cause or applicability.

CVE-2026-46107 · Microsoft / collected KEV context

cve-program · CVE-2026-46107

• https://git.kernel.org/stable/c/b719d12cb94df345e9ad2715fd0abe9afcaeb111
• https://git.kernel.org/stable/c/f49b41c9eb7c6ff00df27cd49cea210abbadd8ad
• https://git.kernel.org/stable/c/f06f6aededd792a754cd677c02b3d3016d868c2c
• https://git.kernel.org/stable/c/12161e03d33afce781f68fa11cc6060538862fad
• https://git.kernel.org/stable/c/323d252a4a378834e4fe68298ca61cfc5dd3a460
• https://git.kernel.org/stable/c/85311a585a26640760cd0f3349ab9f2905691044
• https://git.kernel.org/stable/c/5ec0debbcfd43596e32c1239e993de06a704e04c
• https://git.kernel.org/stable/c/09a65adc7d8bbfce06392cb6d375468e2728ead5

No related operational record is retained in the current change model.