modules: add bad_epoll (CVE-2026-46242, "Bad Epoll" epoll teardown race UAF)

Jaeyoung Chung's kernelCTF "Bad Epoll": a race-condition use-after-free in
fs/eventpoll.c. ep_remove() clears file->f_ep under f_lock but keeps using
the file (hlist_del_rcu + unlock) while a concurrent __fput() frees the
still-referenced struct eventpoll. Reachable by any unprivileged user with
no userns / CONFIG / capability; weaponised via cross-cache to a struct
file, /proc/self/fdinfo arb-read, and ROP. Introduced 58c9b016e128 (6.4),
fixed a6dc643c6931 (7.1-rc1), stable backport 7.0.13. CWE-416; not in KEV.

The corpus's first epoll / VFS-teardown module. Shipped as a reconstructed,
deliberately under-driven trigger on the stackrot / nft_catchall contract:
detect() is a pure version gate (>= 6.4 and below the on-branch fix; no
userns precondition -- epoll needs none); exploit() forks a CPU-pinned
child that exercises the ep_remove-vs-__fput close window a hard-bounded 48
attempts / 2s and returns EXPLOIT_FAIL. It does not grind the race to a
win, does not do the cross-cache reclaim, and does not bundle the fdinfo
R/W + ROP (a won race frees a live struct file and rarely trips KASAN ->
silent-corruption risk).

Wired: registry, Makefile, safety rank (12 -- lowest in the corpus; a
kernel race is the least predictable class), 5 detect() test rows (version
gating), CVE metadata (sorted insert, CWE-416 / T1068 / not-KEV), README +
CVES.md + website counts (44/39), RELEASE_NOTES v0.9.12, and a verify-vm
target (sweep pending). Detection rules are intentionally weak/structural
(epoll ubiquitous, rarely KASAN) -- post-exploitation euid-0 transition,
no yara. Also corrects pre-existing README drift in the "not yet verified"
count (8 -> 11). Not VM-verified, so the verified count stays 28 of 39.
Version 0.9.12. Credit: Jaeyoung Chung (J-jaeyoung).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KUq4DGXSPBmPkAyJ9WnM9n

docs/KEV_CROSSREF.md

@@ -4,7 +4,7 @@ Which SKELETONKEY modules cover CVEs that CISA has observed exploited
 in the wild per the Known Exploited Vulnerabilities catalog.
 Refreshed via `tools/refresh-cve-metadata.py`.
 
-**13 of 38 modules cover KEV-listed CVEs.**
+**13 of 39 modules cover KEV-listed CVEs.**
 
 ## In KEV (prioritize patching)
 
@@ -54,6 +54,7 @@ and are technically reachable. "Not in KEV" is not the same as
 | CVE-2026-31635 | CWE-130 | `dirtydecrypt_cve_2026_31635` |
 | CVE-2026-41651 | CWE-367 | `pack2theroot_cve_2026_41651` |
 | CVE-2026-43494 | ? | `pintheft_cve_2026_43494` |
+| CVE-2026-46242 | CWE-416 | `bad_epoll_cve_2026_46242` |
 | CVE-2026-46243 | CWE-20 | `cifswitch_cve_2026_46243` |
 | CVE-2026-46300 | CWE-787 | `fragnesia_cve_2026_46300` |
 | CVE-2026-46333 | CWE-269 | `ptrace_pidfd_cve_2026_46333` |