Phase 7: PTRACE_TRACEME (CVE-2019-13272) + xt_compat (CVE-2021-22555)

Two famous 2017-2020-era LPEs to broaden 'THE tool for folks'
coverage. Both detect-only initially; exploit ports as follow-ups.

ptrace_traceme (CVE-2019-13272 — jannh @ Google P0, Jun 2019):
- Famous because works on default-config systems with no user_ns
  required — locked-down environments were still vulnerable.
- kernel_range thresholds: 4.4.182 / 4.9.182 / 4.14.131 / 4.19.58 /
  5.0.20 / 5.1.17 / mainline 5.2+
- Exploit shape (deferred): fork → child PTRACE_TRACEME → parent
  execve setuid binary → child ptrace-injects shellcode → root.
- Auditd: flag PTRACE_TRACEME (request 0) — false positives via
  gdb/strace; tune by exclusion.

netfilter_xtcompat (CVE-2021-22555 — Andy Nguyen @ Google P0):
- Bug existed since 2.6.19 (2006) — 15 years of latent vuln. Famous
  for that age + default-config reachability via unprivileged_userns.
- kernel_range thresholds: 4.4.266 / 4.9.266 / 4.14.230 / 4.19.185
  / 5.4.110 / 5.10.27 / 5.11.10 / mainline 5.12+
- detect() probes user_ns+net_ns clone; locked-down → PRECOND_FAIL.
- Exploit shape (deferred): heap massage via msg_msg + sk_buff cross-
  cache groom → kernel R/W → cred or modprobe_path overwrite. ~400
  lines port from Andy's public exploit.c.
- Auditd: unshare + iptables-style setsockopt + msgsnd — combined,
  the canonical exploit footprint.

Both wired into iamroot.c, core/registry.h, Makefile. CVES.md rows
added with detailed status.

Coverage by year now:
  2016: dirty_cow                              🟢
  2019: ptrace_traceme                         🔵
  2021: pwnkit, overlayfs, netfilter_xtcompat  🟢/🟢/🔵
  2022: dirty_pipe, cls_route4                 🟢/🔵
  2023: entrybleed                             🟢
  2024: nf_tables                              🔵
  2026: copy_fail family (×5)                  🟢

Module count: 14. Build clean (no warnings).

core/registry.h

@@ -28,5 +28,7 @@ void iamroot_register_nf_tables(void);
 void iamroot_register_overlayfs(void);
 void iamroot_register_cls_route4(void);
 void iamroot_register_dirty_cow(void);
+void iamroot_register_ptrace_traceme(void);
+void iamroot_register_netfilter_xtcompat(void);
 
 #endif /* IAMROOT_REGISTRY_H */