unix: fix size check in uv_get_process_title()

It was checking that the destination buffer was big enough to hold
the total capacity of the process title (the total storage of argv)
when instead it should be checking that it's big enough to hold
the _current_ process title, which is normally much shorter.

Fixes: https://github.com/libuv/libuv/issues/2666
PR-URL: https://github.com/libuv/libuv/pull/2668
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

src/unix/proctitle.c

@@ -26,7 +26,8 @@
 
 struct uv__process_title {
   char* str;
-  size_t len;
+  size_t len;  /* Length of the current process title. */
+  size_t cap;  /* Maximum capacity. Computed once in uv_setup_args(). */
 };
 
 extern void uv__set_process_title(const char* title);
@@ -52,20 +53,14 @@ char** uv_setup_args(int argc, char** argv) {
   if (argc <= 0)
     return argv;
 
-  /* Calculate how much memory we need for the argv strings. */
-  size = 0;
-  for (i = 0; i < argc; i++)
-    size += strlen(argv[i]) + 1;
-
-#if defined(__MVS__)
-  /* argv is not adjacent. So just use argv[0] */
   pt.str = argv[0];
   pt.len = strlen(argv[0]);
-#else
-  pt.str = argv[0];
-  pt.len = argv[argc - 1] + strlen(argv[argc - 1]) - argv[0];
-  assert(pt.len + 1 == size);  /* argv memory should be adjacent. */
-#endif
+  pt.cap = pt.len + 1;
+
+  /* Calculate how much memory we need for the argv strings. */
+  size = pt.cap;
+  for (i = 1; i < argc; i++)
+    size += strlen(argv[i]) + 1;
 
   /* Add space for the argv pointers. */
   size += (argc + 1) * sizeof(char*);
@@ -75,15 +70,25 @@ char** uv_setup_args(int argc, char** argv) {
     return argv;
 
   /* Copy over the strings and set up the pointer table. */
+  i = 0;
   s = (char*) &new_argv[argc + 1];
-  for (i = 0; i < argc; i++) {
+  size = pt.cap;
+  goto loop;
+
+  for (/* empty */; i < argc; i++) {
     size = strlen(argv[i]) + 1;
+  loop:
     memcpy(s, argv[i], size);
     new_argv[i] = s;
     s += size;
   }
   new_argv[i] = NULL;
 
+  /* argv is not adjacent on z/os, we use just argv[0] on that platform. */
+#ifndef __MVS__
+  pt.cap = argv[i - 1] + size - argv[0];
+#endif
+
   args_mem = new_argv;
   process_title = pt;
 
@@ -92,15 +97,25 @@ char** uv_setup_args(int argc, char** argv) {
 
 
 int uv_set_process_title(const char* title) {
+  struct uv__process_title* pt;
+  size_t len;
+
+  pt = &process_title;
+  len = strlen(title);
+
   uv_once(&process_title_mutex_once, init_process_title_mutex_once);
   uv_mutex_lock(&process_title_mutex);
 
-  if (process_title.len != 0) {
-    /* No need to terminate, byte after is always '\0'. */
-    strncpy(process_title.str, title, process_title.len);
-    uv__set_process_title(title);
+  if (len >= pt->cap) {
+    len = 0;
+    if (pt->cap > 0)
+      len = pt->cap - 1;
   }
 
+  memcpy(pt->str, title, len);
+  memset(pt->str + len, '\0', pt->cap - len);
+  pt->len = len;
+
   uv_mutex_unlock(&process_title_mutex);
 
   return 0;

test/run-tests.c

@@ -45,6 +45,7 @@ int ipc_helper_bind_twice(void);
 int ipc_helper_send_zero(void);
 int stdio_over_pipes_helper(void);
 void spawn_stdin_stdout(void);
+void process_title_big_argv(void);
 int spawn_tcp_server_helper(void);
 
 static int maybe_run_test(int argc, char **argv);
@@ -235,5 +236,11 @@ static int maybe_run_test(int argc, char **argv) {
   }
 #endif  /* !_WIN32 */
 
+  if (strcmp(argv[1], "process_title_big_argv_helper") == 0) {
+    notify_parent_process();
+    process_title_big_argv();
+    return 0;
+  }
+
   return run_test(argv[1], 0, 1);
 }

test/test-list.h

@@ -242,6 +242,7 @@ TEST_DECLARE   (async_null_cb)
 TEST_DECLARE   (eintr_handling)
 TEST_DECLARE   (get_currentexe)
 TEST_DECLARE   (process_title)
+TEST_DECLARE   (process_title_big_argv)
 TEST_DECLARE   (process_title_threadsafe)
 TEST_DECLARE   (cwd_and_chdir)
 TEST_DECLARE   (get_memory)
@@ -788,6 +789,7 @@ TASK_LIST_START
   TEST_ENTRY  (get_currentexe)
 
   TEST_ENTRY  (process_title)
+  TEST_ENTRY  (process_title_big_argv)
   TEST_ENTRY  (process_title_threadsafe)
 
   TEST_ENTRY  (cwd_and_chdir)

test/test-process-title.c

@@ -74,3 +74,62 @@ TEST_IMPL(process_title) {
 
   return 0;
 }
+
+
+static void exit_cb(uv_process_t* process, int64_t status, int signo) {
+  ASSERT(status == 0);
+  ASSERT(signo == 0);
+  uv_close((uv_handle_t*) process, NULL);
+}
+
+
+TEST_IMPL(process_title_big_argv) {
+  uv_process_options_t options;
+  uv_process_t process;
+  size_t exepath_size;
+  char exepath[1024];
+  char jumbo[512];
+  char* args[5];
+
+#ifdef _WIN32
+  /* Remove once https://github.com/libuv/libuv/issues/2667 is fixed. */
+  uv_set_process_title("run-tests");
+#endif
+
+  exepath_size = sizeof(exepath) - 1;
+  ASSERT(0 == uv_exepath(exepath, &exepath_size));
+  exepath[exepath_size] = '\0';
+
+  memset(jumbo, 'x', sizeof(jumbo) - 1);
+  jumbo[sizeof(jumbo) - 1] = '\0';
+
+  /* Note: need to pass three arguments, not two, otherwise
+   * run-tests.c thinks it's the name of a test to run.
+   */
+  args[0] = exepath;
+  args[1] = "process_title_big_argv_helper";
+  args[2] = jumbo;
+  args[3] = jumbo;
+  args[4] = NULL;
+
+  memset(&options, 0, sizeof(options));
+  options.file = exepath;
+  options.args = args;
+  options.exit_cb = exit_cb;
+
+  ASSERT(0 == uv_spawn(uv_default_loop(), &process, &options));
+  ASSERT(0 == uv_run(uv_default_loop(), UV_RUN_DEFAULT));
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}
+
+
+/* Called by process_title_big_argv_helper. */
+void process_title_big_argv(void) {
+  char buf[256] = "fail";
+
+  /* Return value deliberately ignored. */
+  uv_get_process_title(buf, sizeof(buf));
+  ASSERT(0 != strcmp(buf, "fail"));
+}