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gspawn: Audit for async-signal-safety
Functions called between `fork()` and `exec()` have to be async-signal-safe. Add a comment to each function which is called in that context, and `FIXME` comments to the non-async-signal-safe functions which end up being called as leaves of the call graph. The following commits will fix those `FIXME`s. See `man 7 signal-safety`. Signed-off-by: Philip Withnall <withnall@endlessm.com> Helps: #2140
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Philip Withnall
parent
50ce2792ff
commit
0e05ef7750
@ -262,6 +262,9 @@ g_spawn_async (const gchar *working_directory,
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/* Avoids a danger in threaded situations (calling close()
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* on a file descriptor twice, and another thread has
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* re-opened it since the first close)
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*
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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)).
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*/
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static void
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close_and_invalidate (gint *fd)
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@ -270,6 +273,7 @@ close_and_invalidate (gint *fd)
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return;
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else
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{
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/* FIXME: g_close() is not async-signal-safe on failure. */
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(void) g_close (*fd, NULL);
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*fd = -1;
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}
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@ -1081,6 +1085,8 @@ g_spawn_check_exit_status (gint exit_status,
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return ret;
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}
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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)). */
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static gssize
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write_all (gint fd, gconstpointer vbuf, gsize to_write)
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{
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@ -1104,6 +1110,8 @@ write_all (gint fd, gconstpointer vbuf, gsize to_write)
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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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* async-signal-safe (see signal-safety(7)). */
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G_GNUC_NORETURN
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static void
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write_err_and_exit (gint fd, gint msg)
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@ -1116,6 +1124,8 @@ write_err_and_exit (gint fd, gint msg)
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_exit (1);
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}
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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)). */
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static int
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set_cloexec (void *data, gint fd)
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{
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@ -1125,6 +1135,8 @@ set_cloexec (void *data, gint fd)
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return 0;
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}
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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)). */
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static gint
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safe_close (gint fd)
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{
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@ -1137,6 +1149,8 @@ safe_close (gint fd)
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return ret;
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}
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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)). */
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G_GNUC_UNUSED static int
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close_func (void *data, int fd)
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{
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@ -1156,6 +1170,8 @@ struct linux_dirent64
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char d_name[]; /* Filename (null-terminated) */
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};
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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)). */
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static gint
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filename_to_fd (const char *p)
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{
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@ -1169,6 +1185,7 @@ filename_to_fd (const char *p)
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while ((c = *p++) != '\0')
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{
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/* FIXME: g_ascii_isdigit() is not necessarily async-signal-safe. */
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if (!g_ascii_isdigit (c))
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return -1;
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c -= '0';
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@ -1184,6 +1201,8 @@ filename_to_fd (const char *p)
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}
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#endif
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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)). */
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static int
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safe_fdwalk (int (*cb)(void *data, int fd), void *data)
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{
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@ -1237,7 +1256,9 @@ safe_fdwalk (int (*cb)(void *data, int fd), void *data)
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}
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/* If /proc is not mounted or not accessible we fall back to the old
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* rlimit trick */
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* rlimit trick.
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*
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* FIXME: getrlimit() and sysconf() are not async-signal-safe. */
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#endif
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@ -1257,6 +1278,8 @@ safe_fdwalk (int (*cb)(void *data, int fd), void *data)
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#endif
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}
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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)). */
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static void
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safe_closefrom (int lowfd)
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{
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@ -1289,6 +1312,8 @@ safe_closefrom (int lowfd)
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#endif
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}
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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)). */
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static gint
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safe_dup2 (gint fd1, gint fd2)
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{
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@ -1301,6 +1326,8 @@ safe_dup2 (gint fd1, gint fd2)
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return ret;
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}
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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)). */
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static gint
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safe_open (const char *path, gint mode)
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{
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@ -1321,6 +1348,8 @@ enum
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CHILD_FORK_FAILED
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};
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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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do_exec (gint child_err_report_fd,
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gint stdin_fd,
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@ -1358,6 +1387,7 @@ do_exec (gint child_err_report_fd,
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else if (!child_inherits_stdin)
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{
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/* Keep process from blocking on a read of stdin */
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/* FIXME: g_assert() is not async-signal-safe on failure. */
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gint read_null = safe_open ("/dev/null", O_RDONLY);
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g_assert (read_null != -1);
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safe_dup2 (read_null, 0);
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@ -1376,6 +1406,7 @@ do_exec (gint child_err_report_fd,
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}
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else if (stdout_to_null)
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{
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/* FIXME: g_assert() is not async-signal-safe on failure. */
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gint write_null = safe_open ("/dev/null", O_WRONLY);
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g_assert (write_null != -1);
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safe_dup2 (write_null, 1);
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@ -2113,6 +2144,8 @@ cleanup_and_fail:
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/* Based on execvp from GNU C Library */
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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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script_execute (const gchar *file,
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gchar **argv,
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@ -2127,6 +2160,7 @@ script_execute (const gchar *file,
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{
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gchar **new_argv;
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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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new_argv[0] = (char *) "/bin/sh";
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@ -2147,6 +2181,8 @@ script_execute (const gchar *file,
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}
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}
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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)). */
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static gchar*
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my_strchrnul (const gchar *str, gchar c)
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{
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@ -2157,6 +2193,8 @@ my_strchrnul (const gchar *str, gchar c)
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return p;
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}
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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 gint
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g_execute (const gchar *file,
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gchar **argv,
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@ -2190,6 +2228,7 @@ g_execute (const gchar *file,
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gsize len;
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gsize pathlen;
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/* FIXME: getenv() is not async-signal-safe */
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path = NULL;
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if (search_path_from_envp)
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path = g_environ_getenv (envp, "PATH");
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@ -2213,6 +2252,7 @@ g_execute (const gchar *file,
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len = strlen (file) + 1;
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pathlen = strlen (path);
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/* FIXME: malloc() is not async-signal-safe */
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freeme = name = g_malloc (pathlen + len + 1);
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/* Copy the file name at the top, including '\0' */
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