modules: migrate remaining 22 modules to ctx->host fingerprint

Completes the host-fingerprint refactor that started in c00c3b4. Every
module now consults the shared ctx->host (populated once at startup
by core/host.c) instead of re-doing uname / geteuid / /etc/os-release
parsing / fork+unshare(CLONE_NEWUSER) probes per detect().

Migrations applied per module (mechanical, no exploit logic touched):

1. #include "../../core/host.h" inside each module's #ifdef __linux__.
2. kernel_version_current(&v) -> ctx->host->kernel (with the
   v -> v-> arrow-vs-dot fix for all later usage). Drops ~20 redundant
   uname() calls across the corpus.
3. geteuid() == 0 (the 'already root, nothing to escalate' gate) ->
   bool is_root = ctx->host ? ctx->host->is_root : (geteuid() == 0);
   This is the key change that lets the unit test suite construct
   non-root fingerprints regardless of the test process's actual euid.
4. Per-detect fork+unshare(CLONE_NEWUSER) probe helpers (named
   can_unshare_userns / can_unshare_userns_mount across the corpus)
   are removed wholesale; their call sites now consult
   ctx->host->unprivileged_userns_allowed, which was probed once at
   startup. Removes ~10 per-scan fork()s.

Modules touched by this commit (22):

  Batch A (7): dirty_pipe, dirty_cow, ptrace_traceme, pwnkit,
               cgroup_release_agent, overlayfs_setuid, and entrybleed
               (no migration target — KPTI gate stays as direct sysfs
               read; documented as 'no applicable pattern').

  Batch B (7): nf_tables, cls_route4, netfilter_xtcompat, af_packet,
               af_packet2, af_unix_gc, fuse_legacy.

  Batch C (8): stackrot, nft_set_uaf, nft_fwd_dup, nft_payload,
               sudo_samedit, sequoia, sudoedit_editor, vmwgfx.

Combined with the 4 modules already migrated (dirtydecrypt, fragnesia,
pack2theroot, overlayfs) and the 5-module copy_fail_family bridge,
the entire registered corpus now goes through ctx->host. The 4
'fork+unshare per detect()' helpers that existed across nf_tables,
cls_route4, netfilter_xtcompat, af_packet, af_packet2, fuse_legacy,
nft_set_uaf, nft_fwd_dup, nft_payload, sequoia,
cgroup_release_agent, and overlayfs_setuid are now gone — replaced by
the single startup probe in core/host.c.

Verification:
- Linux (docker gcc:latest + libglib2.0-dev): full clean build links
  31 modules; tests/test_detect.c: 8/8 pass.
- macOS (local): full clean build links 31 modules (Mach-O, 172KB);
  test suite reports skipped as designed on non-Linux.

Subsequent commits can add more EXPECT_DETECT cases in
tests/test_detect.c — the host-fingerprint paths in every module are
now uniformly testable via synthetic struct skeletonkey_host instances.

modules/stackrot_cve_2023_3269/skeletonkey_modules.c

@@ -72,6 +72,7 @@
 #include "../../core/kernel_range.h"
 #include "../../core/offsets.h"
 #include "../../core/finisher.h"
+#include "../../core/host.h"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -150,31 +151,31 @@ static bool maple_tree_variant_present(const struct kernel_version *v)
 
 static skeletonkey_result_t stackrot_detect(const struct skeletonkey_ctx *ctx)
 {
-    struct kernel_version v;
-    if (!kernel_version_current(&v)) {
-        fprintf(stderr, "[!] stackrot: could not parse kernel version\n");
+    const struct kernel_version *v = ctx->host ? &ctx->host->kernel : NULL;
+    if (!v || v->major == 0) {
+        if (!ctx->json) fprintf(stderr, "[!] stackrot: host fingerprint missing kernel version — bailing\n");
         return SKELETONKEY_TEST_ERROR;
     }
 
     /* Bug introduced in 6.1 (when maple tree landed). Pre-6.1 kernels
      * use rbtree-based VMAs and don't have this bug. */
-    if (v.major < 6 || (v.major == 6 && v.minor < 1)) {
+    if (v->major < 6 || (v->major == 6 && v->minor < 1)) {
         if (!ctx->json) {
             fprintf(stderr, "[+] stackrot: kernel %s predates maple-tree VMA code (introduced in 6.1)\n",
-                    v.release);
+                    v->release);
         }
         return SKELETONKEY_OK;
     }
 
-    bool patched = kernel_range_is_patched(&stackrot_range, &v);
+    bool patched = kernel_range_is_patched(&stackrot_range, v);
     if (patched) {
         if (!ctx->json) {
-            fprintf(stderr, "[+] stackrot: kernel %s is patched\n", v.release);
+            fprintf(stderr, "[+] stackrot: kernel %s is patched\n", v->release);
         }
         return SKELETONKEY_OK;
     }
     if (!ctx->json) {
-        fprintf(stderr, "[!] stackrot: kernel %s in vulnerable range\n", v.release);
+        fprintf(stderr, "[!] stackrot: kernel %s in vulnerable range\n", v->release);
         fprintf(stderr, "[i] stackrot: mm-class bug — affects default-config kernels; "
                         "no exotic preconditions\n");
     }
@@ -631,7 +632,8 @@ static skeletonkey_result_t stackrot_exploit_linux(const struct skeletonkey_ctx
         fprintf(stderr, "[-] stackrot: detect() says not vulnerable; refusing\n");
         return pre;
     }
-    if (geteuid() == 0) {
+    bool is_root = ctx->host ? ctx->host->is_root : (geteuid() == 0);
+    if (is_root) {
         fprintf(stderr, "[i] stackrot: already root — nothing to escalate\n");
         return SKELETONKEY_OK;
     }
@@ -641,8 +643,8 @@ static skeletonkey_result_t stackrot_exploit_linux(const struct skeletonkey_ctx
         return SKELETONKEY_PRECOND_FAIL;
     }
     {
-        struct kernel_version v;
-        if (!kernel_version_current(&v) || !maple_tree_variant_present(&v)) {
+        const struct kernel_version *v = ctx->host ? &ctx->host->kernel : NULL;
+        if (!v || v->major == 0 || !maple_tree_variant_present(v)) {
             fprintf(stderr, "[-] stackrot: maple-tree variant not detectable\n");
             return SKELETONKEY_PRECOND_FAIL;
         }