Don't allow cloning root nodes

The root nodes are /system and /vendor. Adding new files into these
directories, although works on some devices, mostly bootloops on many
devices out there. So don't allow it, which also makes the whole magic
mounting logic much easier and extensible.

native/jni/core/bootstages.cpp

@@ -28,7 +28,6 @@ using namespace std;
 
 static char buf[PATH_MAX], buf2[PATH_MAX];
 static vector<string> module_list;
-static bool seperate_vendor;
 static bool no_secure_dir = false;
 
 static int bind_mount(const char *from, const char *to, bool log = true);
@@ -76,7 +75,8 @@ class node_entry {
 		this->parent = parent;
 		this->module = module;
 	}
-	bool is_vendor();
+	bool is_special();
+	bool is_root();
 	string get_path();
 	void insert(node_entry *&);
 	void clone_skeleton();
@@ -88,10 +88,14 @@ node_entry::~node_entry() {
 		delete node;
 }
 
-bool node_entry::is_vendor() {
+bool node_entry::is_special() {
 	return parent ? (parent->parent ? false : name == "vendor") : false;
 }
 
+bool node_entry::is_root() {
+	return parent ? (parent->parent ? false : name == "vendor") : true;
+}
+
 string node_entry::get_path() {
 	get_path(buf);
 	return buf;
@@ -140,35 +144,45 @@ void node_entry::create_module_tree(const char *module) {
 
 		// buf = real path, buf2 = module path
 		snprintf(buf, PATH_MAX, "%s/%s", full_path.c_str(), entry->d_name);
-		int eo2 = snprintf(buf2, PATH_MAX, MODULEROOT "/%s%s/%s",
+		int eof = snprintf(buf2, PATH_MAX, MODULEROOT "/%s%s/%s",
 				module, full_path.c_str(), entry->d_name);
 
 		/*
-		 * Clone the parent in the following condition:
-		 * 1. File in module is a symlink
-		 * 2. Target file do not exist
-		 * 3. Target file is a symlink (exclude /system/vendor)
+		 * Clone current node directory in the following condition:
+		 * 1. We are not a root node
+		 * 2. Target does not exist or
+		 * 3. Module file is a symlink or
+		 * 4. Target file is a symlink (exclude special nodes)
 		 */
 		bool clone = false;
 		if (IS_LNK(node) || access(buf, F_OK) == -1) {
 			clone = true;
-		} else if (!node->is_vendor()) {
+		} else if (!node->is_special()) {
 			struct stat s;
-			xstat(buf, &s);
+			xlstat(buf, &s);
 			if (S_ISLNK(s.st_mode))
 				clone = true;
 		}
+		if (clone && is_root()) {
+			// Remove both the new node and file that requires cloning ourselves
+			rm_rf(buf2);
+			delete node;
+			continue;
+		}
 
 		if (clone) {
 			// Mark self as a skeleton
 			status |= IS_SKEL;  /* This will not overwrite if parent is module */
 			node->status = IS_MODULE;
+		} else if (node->is_special()) {
+			// Special nodes will be pulled out as root nodes later
+			node->status = IS_INTER;
 		} else {
 			// Clone attributes from real path
 			clone_attr(buf, buf2);
 			if (IS_DIR(node)) {
 				// Check if marked as replace
-				strcpy(buf2 + eo2, "/.replace");
+				strcpy(buf2 + eof, "/.replace");
 				if (access(buf2, F_OK) == 0) {
 					// Replace everything, mark as leaf
 					node->status = IS_MODULE;
@@ -227,14 +241,7 @@ void node_entry::clone_skeleton() {
 			close(creat(buf, 0644));
 		// Links will be handled later
 
-		if (child->is_vendor()) {
-			if (seperate_vendor) {
-				cp_afc(MIRRDIR "/system/vendor", "/system/vendor");
-				VLOGI("copy_link ", "/system/vendor", MIRRDIR "/system/vendor");
-			}
-			// Skip
-			continue;
-		} else if (child->status & IS_MODULE) {
+		if (child->status & IS_MODULE) {
 			// Mount from module file to dummy file
 			snprintf(buf2, PATH_MAX, "%s/%s%s/%s", MODULEMNT,
 					 child->module, full_path.c_str(), child->name.c_str());
@@ -272,19 +279,16 @@ void node_entry::magic_mount() {
 		for (auto &child : children)
 			child->magic_mount();
 	}
-	// The only thing goes here should be placeholder nodes
-	// There should be no dummies, so don't need to handle it here
 }
 
 node_entry *node_entry::extract(const char *name) {
 	node_entry *node = nullptr;
-	// Extract the node out and swap with placeholder
-	for (auto &child : children) {
-		if (child->name == name) {
-			node = child;
-			child = new node_entry(name);
-			child->parent = node->parent;
+	// Extract the node out of the tree
+	for (auto it = children.begin(); it != children.end(); ++it) {
+		if ((*it)->name == name) {
+			node = *it;
 			node->parent = nullptr;
+			children.erase(it);
 			break;
 		}
 	}
@@ -364,12 +368,12 @@ static bool magisk_env() {
 		if (str_contains(line, " /system_root ")) {
 			mount_mirror(system_root, MS_RDONLY);
 			xsymlink(MIRRMNT(system_root) "/system", MIRRMNT(system));
+			VLOGI("link", MIRRMNT(system_root) "/system", MIRRMNT(system));
 			system_as_root = true;
 		} else if (!system_as_root && str_contains(line, " /system ")) {
 			mount_mirror(system, MS_RDONLY);
 		} else if (str_contains(line, " /vendor ")) {
 			mount_mirror(vendor, MS_RDONLY);
-			seperate_vendor = true;
 		} else if (str_contains(line, " /data ")) {
 			mount_mirror(data, 0);
 		} else if (SDK_INT >= 24 &&
@@ -379,9 +383,9 @@ static bool magisk_env() {
 		}
 		return true;
 	});
-	if (!seperate_vendor) {
-		xsymlink(MIRRDIR "/system/vendor", MIRRDIR "/vendor");
-		VLOGI("link", MIRRDIR "/system/vendor", MIRRDIR "/vendor");
+	if (access(MIRRMNT(vendor), F_OK) != 0) {
+		xsymlink(MIRRMNT(system) "/vendor", MIRRMNT(vendor));
+		VLOGI("link", MIRRMNT(system) "/vendor", MIRRMNT(vendor));
 	}
 
 	// Disable/remove magiskhide, resetprop, and modules
@@ -622,9 +626,6 @@ void post_fs_data(int client) {
 	// Create the system root entry
 	auto sys_root = new node_entry("system", IS_INTER);
 
-	// Vendor root entry
-	node_entry *ven_root = nullptr;
-
 	bool has_modules = false;
 
 	LOGI("* Loading modules\n");
@@ -659,17 +660,18 @@ void post_fs_data(int client) {
 	}
 
 	if (has_modules) {
-		// Pull out /system/vendor node if exist
-		ven_root = sys_root->extract("vendor");
+		// Pull out special nodes if exist
+		node_entry *special;
+		if ((special = sys_root->extract("vendor"))) {
+			special->magic_mount();
+			delete special;
+		}
 
-		// Magic!!
 		sys_root->magic_mount();
-		if (ven_root) ven_root->magic_mount();
 	}
 
 	// Cleanup memory
 	delete sys_root;
-	delete ven_root;
 
 	core_only();
 }