add: implement function to check for printable C strings in namecache entry

Author: jurre111

lara/kexploit/vfs.m

@@ -238,14 +238,33 @@ static uint64_t nclookupchild(uint64_t dir_vn, const char *comp) {
 }
 
 // Fallback: scan a namecache entry structure for any plausible name pointer.
+static bool is_printable_cstring(const char *buf, size_t len) {
+    if (len == 0) return false;
+    size_t i = 0;
+    // must be null-terminated somewhere within len
+    bool seen_print = false;
+    for (; i < len; i++) {
+        unsigned char c = (unsigned char)buf[i];
+        if (c == 0) break;
+        if (c < 0x20 || c > 0x7e) return false;
+        seen_print = true;
+    }
+    return seen_print && i < len; // terminated and had printable chars
+}
+
 static uint64_t ncentry_find_name_ptr(uint64_t nc, int *found_off) {
-    for (int off = 0; off < 0x80; off += 8) {
+    // Scan a larger window within the namecache entry for any pointer-like value
+    for (int off = 0; off < 0x200; off += 8) {
         uint64_t val = kr64(nc + off);
         if (!iskpointer(val)) continue;
-        char nm[4];
-        krd(val, nm, 3); nm[3] = 0;
-        // check for printable ascii start
-        if ((unsigned char)nm[0] >= 0x20 && (unsigned char)nm[0] <= 0x7e) {
+
+        // read up to 128 bytes from candidate pointer
+        char buf[128];
+        memset(buf, 0, sizeof(buf));
+        // krd may fail silently; guard with small reads
+        krd(val, buf, sizeof(buf));
+
+        if (is_printable_cstring(buf, sizeof(buf))) {
             if (found_off) *found_off = off;
             return val;
         }