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

core/cve_metadata.c

@@ -292,6 +292,14 @@ const struct cve_metadata cve_metadata_table[] = {
         .in_kev              = false,
         .kev_date_added      = "",
     },
+    {
+        .cve                 = "CVE-2026-46242",
+        .cwe                 = "CWE-416",
+        .attack_technique    = "T1068",
+        .attack_subtechnique = NULL,
+        .in_kev              = false,
+        .kev_date_added      = "",
+    },
     {
         .cve                 = "CVE-2026-46243",
         .cwe                 = "CWE-20",

core/registry.h

@@ -59,6 +59,7 @@ void skeletonkey_register_ptrace_pidfd(void);
 void skeletonkey_register_sudo_host(void);
 void skeletonkey_register_cifswitch(void);
 void skeletonkey_register_nft_catchall(void);
+void skeletonkey_register_bad_epoll(void);
 
 /* Call every skeletonkey_register_<family>() above in canonical order.
  * Single source of truth so the main binary and the test binary stay

core/registry_all.c

@@ -55,4 +55,5 @@ void skeletonkey_register_all_modules(void)
     skeletonkey_register_sudo_host();
     skeletonkey_register_cifswitch();
     skeletonkey_register_nft_catchall();
+    skeletonkey_register_bad_epoll();
 }