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gspawn: Don’t use malloc() when running a binary under /bin/sh
Allocate a working buffer before calling `fork()` to avoid calling `malloc()` in the async-signal-safe context between `fork()` and `exec()`, where it’s not safe to use. In this case, the buffer is used to assemble a wrapper around `argv` so it can be run under `/bin/sh`. See `man 7 signal-safety`. Signed-off-by: Philip Withnall <withnall@endlessm.com> Fixes: #2140
This commit is contained in:
Philip Withnall
parent
cf5af28169
commit
dd36248f9e
@ -159,6 +159,8 @@ static gint safe_close (gint fd);
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static gint g_execute (const gchar *file,
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gchar **argv,
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gchar **argv_buffer,
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gsize argv_buffer_len,
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gchar **envp,
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const gchar *search_path,
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gchar *search_path_buffer,
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@ -1374,6 +1376,8 @@ do_exec (gint child_err_report_fd,
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gint stderr_fd,
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const gchar *working_directory,
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gchar **argv,
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gchar **argv_buffer,
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gsize argv_buffer_len,
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gchar **envp,
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gboolean close_descriptors,
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const gchar *search_path,
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@ -1483,6 +1487,7 @@ do_exec (gint child_err_report_fd,
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g_execute (argv[0],
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file_and_argv_zero ? argv + 1 : argv,
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argv_buffer, argv_buffer_len,
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envp, search_path, search_path_buffer, search_path_buffer_len);
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/* Exec failed */
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@ -1748,6 +1753,8 @@ fork_exec_with_fds (gboolean intermediate_child,
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const gchar *chosen_search_path;
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gchar *search_path_buffer = NULL;
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gsize search_path_buffer_len = 0;
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gchar **argv_buffer = NULL;
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gsize argv_buffer_len = 0;
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#ifdef POSIX_SPAWN_AVAILABLE
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if (!intermediate_child && working_directory == NULL && !close_descriptors &&
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@ -1830,9 +1837,16 @@ fork_exec_with_fds (gboolean intermediate_child,
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search_path_buffer_len = strlen (chosen_search_path) + strlen (argv[0]) + 2;
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search_path_buffer = g_malloc (search_path_buffer_len);
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/* And allocate a buffer which is 2 elements longer than @argv, so that if
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* script_execute() has to be called later on, it can build a wrapper argv
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* array in this buffer. */
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argv_buffer_len = g_strv_length (argv) + 2;
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argv_buffer = g_new (gchar *, argv_buffer_len);
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if (!g_unix_open_pipe (child_err_report_pipe, pipe_flags, error))
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{
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g_free (search_path_buffer);
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g_free (argv_buffer);
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return FALSE;
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}
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@ -1912,6 +1926,8 @@ fork_exec_with_fds (gboolean intermediate_child,
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stderr_fd,
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working_directory,
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argv,
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argv_buffer,
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argv_buffer_len,
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envp,
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close_descriptors,
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chosen_search_path,
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@ -1943,6 +1959,8 @@ fork_exec_with_fds (gboolean intermediate_child,
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stderr_fd,
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working_directory,
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argv,
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argv_buffer,
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argv_buffer_len,
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envp,
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close_descriptors,
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chosen_search_path,
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@ -2076,6 +2094,7 @@ fork_exec_with_fds (gboolean intermediate_child,
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close_and_invalidate (&child_pid_report_pipe[0]);
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g_free (search_path_buffer);
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g_free (argv_buffer);
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if (child_pid)
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*child_pid = pid;
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@ -2110,6 +2129,7 @@ fork_exec_with_fds (gboolean intermediate_child,
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close_and_invalidate (&child_pid_report_pipe[1]);
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g_free (search_path_buffer);
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g_free (argv_buffer);
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return FALSE;
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}
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@ -2210,9 +2230,11 @@ cleanup_and_fail:
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/* This function is called between fork() and exec() and hence must be
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* async-signal-safe (see signal-safety(7)) until it calls exec(). */
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static void
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static gboolean
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script_execute (const gchar *file,
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gchar **argv,
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gchar **argv_buffer,
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gsize argv_buffer_len,
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gchar **envp)
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{
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/* Count the arguments. */
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@ -2220,29 +2242,25 @@ script_execute (const gchar *file,
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while (argv[argc])
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++argc;
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/* Construct an argument list for the shell. */
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{
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gchar **new_argv;
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/* Construct an argument list for the shell. */
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if (argc + 2 > argv_buffer_len)
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return FALSE;
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/* FIXME: This is not async-signal-safe */
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new_argv = g_new0 (gchar*, argc + 2); /* /bin/sh and NULL */
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argv_buffer[0] = (char *) "/bin/sh";
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argv_buffer[1] = (char *) file;
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while (argc > 0)
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{
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argv_buffer[argc + 1] = argv[argc];
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--argc;
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}
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new_argv[0] = (char *) "/bin/sh";
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new_argv[1] = (char *) file;
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while (argc > 0)
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{
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new_argv[argc + 1] = argv[argc];
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--argc;
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}
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/* Execute the shell. */
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if (envp)
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execve (argv_buffer[0], argv_buffer, envp);
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else
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execv (argv_buffer[0], argv_buffer);
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/* Execute the shell. */
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if (envp)
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execve (new_argv[0], new_argv, envp);
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else
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execv (new_argv[0], new_argv);
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g_free (new_argv);
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}
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return TRUE;
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}
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/* This function is called between fork() and exec() and hence must be
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@ -2262,6 +2280,8 @@ my_strchrnul (const gchar *str, gchar c)
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static gint
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g_execute (const gchar *file,
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gchar **argv,
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gchar **argv_buffer,
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gsize argv_buffer_len,
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gchar **envp,
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const gchar *search_path,
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gchar *search_path_buffer,
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@ -2282,8 +2302,12 @@ g_execute (const gchar *file,
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else
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execv (file, argv);
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if (errno == ENOEXEC)
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script_execute (file, argv, envp);
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if (errno == ENOEXEC &&
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!script_execute (file, argv, argv_buffer, argv_buffer_len, envp))
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{
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errno = ENOMEM;
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return -1;
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}
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}
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else
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{
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@ -2332,8 +2356,12 @@ g_execute (const gchar *file,
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else
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execv (startp, argv);
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if (errno == ENOEXEC)
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script_execute (startp, argv, envp);
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if (errno == ENOEXEC &&
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!script_execute (startp, argv, argv_buffer, argv_buffer_len, envp))
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{
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errno = ENOMEM;
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return -1;
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}
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switch (errno)
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{
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