fix: sending 32-bit int instead of 8-bit; fix: fd leak

This commit fixes the issue where a 32-bit (int) number was sent instead of a 8-bit (uint8_t) number. Also fixes a fd leak when connecting to the companion.

zygiskd/src/companion.c

@@ -42,28 +42,16 @@ void *entry_thread(void *arg) {
   int fd = args->fd;
   zygisk_companion_entry_func module_entry = args->entry;
 
-  struct stat st0;
-  fstat(fd, &st0);
-
   LOGI("New companion thread (inside the thread!).\n - Client fd: %d\n", fd);
 
   module_entry(fd);
 
-  /* TODO: Is this even necessary? */
-  struct stat st1;
-  if (fstat(fd, &st1) != -1) {
-    if (st0.st_dev != st1.st_dev || st0.st_ino != st1.st_ino) {
-      close(fd);
-
-      LOGI("Client fd has been replaced. Bye!\n");
-    }
-  }
+  LOGI("Companion thread has been terminated.\n");
 
+  close(fd);
   free(args);
 
   pthread_exit(NULL);
-
-  return NULL;
 }
 
 void entry(int fd) {
@@ -74,20 +62,18 @@ void entry(int fd) {
   if (ret == -1) {
     LOGE("Failed to read module name\n");
 
-    uint8_t response = 2;
-    write(fd, &response, sizeof(response));
+    write_uint8_t(fd, 2);
 
     exit(0);
   }
 
   LOGI(" - Module name: `%.*s`\n", (int)ret, name);
 
-  int library_fd = gread_fd(fd);
+  int library_fd = read_fd(fd);
   if (library_fd == -1) {
     LOGE("Failed to receive library fd\n");
 
-    uint8_t response = 2;
-    write(fd, &response, sizeof(response));
+    write_uint8_t(fd, 2);
 
     exit(0);
   }
@@ -100,11 +86,11 @@ void entry(int fd) {
   if (module_entry == NULL) {
     LOGI("No companion module entry for module: %.*s\n", (int)ret, name);
 
-    write_int(fd, 0);
+    write_uint8_t(fd, 0);
 
     exit(0);
   } else {
-    write_int(fd, 1);
+    write_uint8_t(fd, 1);
   }
 
   while (1) {
@@ -119,7 +105,7 @@ void entry(int fd) {
     struct companion_module_thread_args *args = malloc(sizeof(struct companion_module_thread_args));
     args->entry = module_entry;
   
-    if ((args->fd = gread_fd(fd)) == -1) {
+    if ((args->fd = read_fd(fd)) == -1) {
       LOGE("Failed to receive client fd\n");
 
       exit(0);

zygiskd/src/utils.c

@@ -192,7 +192,7 @@ int unix_listener_from_path(char *restrict path) {
   return socket_fd;
 }
 
-ssize_t gwrite_fd(int fd, int sendfd) {
+ssize_t write_fd(int fd, int sendfd) {
   char cmsgbuf[CMSG_SPACE(sizeof(int))];
   char buf[1] = { 0 };
   
@@ -225,7 +225,7 @@ ssize_t gwrite_fd(int fd, int sendfd) {
   return ret;
 }
 
-int gread_fd(int fd) {
+int read_fd(int fd) {
   char cmsgbuf[CMSG_SPACE(sizeof(int))];
   char buf[1] = { 0 };
   

zygiskd/src/utils.h

@@ -36,9 +36,8 @@ int chcon(const char *path, const char *restrict context);
 
 int unix_listener_from_path(char *path);
 
-ssize_t gwrite_fd(int fd, int sendfd);
-
-int gread_fd(int fd);
+ssize_t write_fd(int fd, int sendfd);
+int read_fd(int fd);
 
 write_func_def(int);
 read_func_def(int);

zygiskd/src/zygiskd.c

@@ -278,7 +278,7 @@ static int spawn_companion(char *restrict argv[], char *restrict name, int lib_f
 
         return -1;
       }
-      if (gwrite_fd(daemon_fd, lib_fd) == -1) {
+      if (write_fd(daemon_fd, lib_fd) == -1) {
         LOGE("Failed sending library fd.\n");
 
         close(daemon_fd);
@@ -694,7 +694,7 @@ void zygiskd_start(char *restrict argv[]) {
 
         for (size_t i = 0; i < clen; i++) {
           if (write_string(client_fd, context.modules[i].name) == -1) break;
-          if (gwrite_fd(client_fd, context.modules[i].lib_fd) == -1) break;
+          if (write_fd(client_fd, context.modules[i].lib_fd) == -1) break;
         }
 
         LOGI("ZD++ ReadModules\n");
@@ -711,6 +711,8 @@ void zygiskd_start(char *restrict argv[]) {
         struct Module *module = &context.modules[index];
 
         if (module->companion != -1) {
+          LOGI("  Polling companion for module \"%s\"\n", module->name);
+
           if (!check_unix_socket(module->companion, false)) {
             LOGE("  Poll companion for module \"%s\" crashed\n", module->name);
 
@@ -733,22 +735,32 @@ void zygiskd_start(char *restrict argv[]) {
           }
         }
 
+        /* 
+          INFO: Companion already exists or was created. In any way,
+                 it should be in the while loop to receive fds now,
+                 so just sending the file descriptor of the client is
+                 safe.
+        */
         if (module->companion != -1) {
-          if (gwrite_fd(module->companion, client_fd) == -1) {
+          LOGI("  Sending companion fd socket of module \"%s\"\n", module->name);
+
+          if (write_fd(module->companion, client_fd) == -1) {
             LOGE("Failed to send companion fd socket of module \"%s\"\n", module->name);
 
-            ret = write_int(client_fd, 0);
+            ret = write_uint8_t(client_fd, 0);
             ASSURE_SIZE_WRITE_BREAK("RequestCompanionSocket", "response", ret, sizeof(int));
 
             close(module->companion);
             module->companion = -1;
 
+            /* INFO: RequestCompanionSocket by defailt doesn't close the client_fd */
             close(client_fd);
           }
         } else {
-          ret = write_int(client_fd, 0);
+          ret = write_uint8_t(client_fd, 0);
           ASSURE_SIZE_WRITE_BREAK("RequestCompanionSocket", "response", ret, sizeof(int));
 
+          /* INFO: RequestCompanionSocket by defailt doesn't close the client_fd */
           close(client_fd);
         }
 
@@ -781,7 +793,7 @@ void zygiskd_start(char *restrict argv[]) {
           break;
         }
 
-        if (gwrite_fd(client_fd, fd) == -1) {
+        if (write_fd(client_fd, fd) == -1) {
           LOGE("Failed sending module directory \"%s\" fd: %s\n", module_dir, strerror(errno));
 
           close(fd);