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https://gitlab.gnome.org/GNOME/glib.git
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Merge branch '2140-spawn-async-signal-safety' into 'master'
Resolve "calling malloc in fork child is undefined-behaviour" Closes #2140 See merge request GNOME/glib!1544
This commit is contained in:
Sebastian Dröge
commit
e48e1447e6
284
glib/gspawn.c
284
glib/gspawn.c
@ -155,12 +155,16 @@ extern char **environ;
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*/
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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 **envp,
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gboolean search_path,
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gboolean search_path_from_envp);
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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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gsize search_path_buffer_len);
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static gboolean fork_exec_with_pipes (gboolean intermediate_child,
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const gchar *working_directory,
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@ -262,6 +266,9 @@ 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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@ -270,7 +277,7 @@ close_and_invalidate (gint *fd)
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return;
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else
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{
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(void) g_close (*fd, NULL);
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safe_close (*fd);
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*fd = -1;
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}
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}
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@ -1081,6 +1088,8 @@ 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 +1113,8 @@ 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 +1127,8 @@ 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 +1138,8 @@ 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 +1152,8 @@ 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 +1173,8 @@ 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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@ -1169,7 +1188,7 @@ filename_to_fd (const char *p)
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while ((c = *p++) != '\0')
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{
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if (!g_ascii_isdigit (c))
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if (c < '0' || c > '9')
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return -1;
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c -= '0';
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@ -1184,6 +1203,8 @@ 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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@ -1200,11 +1221,11 @@ safe_fdwalk (int (*cb)(void *data, int fd), void *data)
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* may be slow on non-Linux operating systems, especially on systems allowing
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* very high number of open file descriptors.
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*/
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gint open_max;
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gint open_max = -1;
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gint fd;
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gint res = 0;
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#ifdef HAVE_SYS_RESOURCE_H
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#if 0 && defined(HAVE_SYS_RESOURCE_H)
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struct rlimit rl;
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#endif
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@ -1237,17 +1258,36 @@ 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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#endif
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#ifdef HAVE_SYS_RESOURCE_H
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if (getrlimit(RLIMIT_NOFILE, &rl) == 0 && rl.rlim_max != RLIM_INFINITY)
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open_max = rl.rlim_max;
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else
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#if 0 && defined(HAVE_SYS_RESOURCE_H)
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/* Use getrlimit() function provided by the system if it is known to be
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* async-signal safe.
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*
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* Currently there are no operating systems known to provide a safe
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* implementation, so this section is not used for now.
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*/
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if (getrlimit (RLIMIT_NOFILE, &rl) == 0 && rl.rlim_max != RLIM_INFINITY)
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open_max = rl.rlim_max;
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#endif
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open_max = sysconf (_SC_OPEN_MAX);
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#if defined(__FreeBSD__) || defined(__OpenBSD__)
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/* Use sysconf() function provided by the system if it is known to be
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* async-signal safe.
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*
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* FreeBSD: sysconf() is included in the list of async-signal safe functions
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* found in https://man.freebsd.org/sigaction(2).
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*
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* OpenBSD: sysconf() is included in the list of async-signal safe functions
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* found in https://man.openbsd.org/sigaction.2.
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*/
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if (open_max < 0)
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open_max = sysconf (_SC_OPEN_MAX);
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#endif
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/* Hardcoded fallback: the default process hard limit in Linux as of 2020 */
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if (open_max < 0)
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open_max = 4096;
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for (fd = 0; fd < open_max; fd++)
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if ((res = cb (data, fd)) != 0)
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@ -1257,6 +1297,8 @@ 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 +1331,8 @@ 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 +1345,8 @@ 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 +1367,8 @@ 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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@ -1328,10 +1376,13 @@ 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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gboolean search_path,
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gboolean search_path_from_envp,
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const gchar *search_path,
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gchar *search_path_buffer,
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gsize search_path_buffer_len,
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gboolean stdout_to_null,
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gboolean stderr_to_null,
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gboolean child_inherits_stdin,
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@ -1359,7 +1410,9 @@ do_exec (gint child_err_report_fd,
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{
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/* Keep process from blocking on a read of stdin */
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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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if (read_null < 0)
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write_err_and_exit (child_err_report_fd,
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CHILD_DUP2_FAILED);
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safe_dup2 (read_null, 0);
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close_and_invalidate (&read_null);
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}
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@ -1377,7 +1430,9 @@ do_exec (gint child_err_report_fd,
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else if (stdout_to_null)
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{
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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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if (write_null < 0)
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write_err_and_exit (child_err_report_fd,
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CHILD_DUP2_FAILED);
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safe_dup2 (write_null, 1);
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close_and_invalidate (&write_null);
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}
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@ -1432,7 +1487,8 @@ 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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envp, search_path, search_path_from_envp);
|
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argv_buffer, argv_buffer_len,
|
||||
envp, search_path, search_path_buffer, search_path_buffer_len);
|
||||
|
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/* Exec failed */
|
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write_err_and_exit (child_err_report_fd,
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@ -1694,6 +1750,11 @@ fork_exec_with_fds (gboolean intermediate_child,
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gint child_pid_report_pipe[2] = { -1, -1 };
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guint pipe_flags = cloexec_pipes ? FD_CLOEXEC : 0;
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gint status;
|
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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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@ -1744,8 +1805,50 @@ fork_exec_with_fds (gboolean intermediate_child,
|
||||
}
|
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#endif /* POSIX_SPAWN_AVAILABLE */
|
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|
||||
/* Choose a search path. This has to be done before calling fork()
|
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* as getenv() isn’t async-signal-safe (see `man 7 signal-safety`). */
|
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chosen_search_path = NULL;
|
||||
if (search_path_from_envp)
|
||||
chosen_search_path = g_environ_getenv (envp, "PATH");
|
||||
if (search_path && chosen_search_path == NULL)
|
||||
chosen_search_path = g_getenv ("PATH");
|
||||
|
||||
if (chosen_search_path == NULL)
|
||||
{
|
||||
/* There is no 'PATH' in the environment. The default
|
||||
* * search path in libc is the current directory followed by
|
||||
* * the path 'confstr' returns for '_CS_PATH'.
|
||||
* */
|
||||
|
||||
/* In GLib we put . last, for security, and don't use the
|
||||
* * unportable confstr(); UNIX98 does not actually specify
|
||||
* * what to search if PATH is unset. POSIX may, dunno.
|
||||
* */
|
||||
|
||||
chosen_search_path = "/bin:/usr/bin:.";
|
||||
}
|
||||
|
||||
/* Allocate a buffer which the fork()ed child can use to assemble potential
|
||||
* paths for the binary to exec(), combining the argv[0] and elements from
|
||||
* the chosen_search_path. This can’t be done in the child because malloc()
|
||||
* (or alloca()) are not async-signal-safe (see `man 7 signal-safety`).
|
||||
*
|
||||
* Add 2 for the nul terminator and a leading `/`. */
|
||||
search_path_buffer_len = strlen (chosen_search_path) + strlen (argv[0]) + 2;
|
||||
search_path_buffer = g_malloc (search_path_buffer_len);
|
||||
|
||||
/* And allocate a buffer which is 2 elements longer than @argv, so that if
|
||||
* script_execute() has to be called later on, it can build a wrapper argv
|
||||
* array in this buffer. */
|
||||
argv_buffer_len = g_strv_length (argv) + 2;
|
||||
argv_buffer = g_new (gchar *, argv_buffer_len);
|
||||
|
||||
if (!g_unix_open_pipe (child_err_report_pipe, pipe_flags, error))
|
||||
return FALSE;
|
||||
{
|
||||
g_free (search_path_buffer);
|
||||
g_free (argv_buffer);
|
||||
return FALSE;
|
||||
}
|
||||
|
||||
if (intermediate_child && !g_unix_open_pipe (child_pid_report_pipe, pipe_flags, error))
|
||||
goto cleanup_and_fail;
|
||||
@ -1823,10 +1926,13 @@ fork_exec_with_fds (gboolean intermediate_child,
|
||||
stderr_fd,
|
||||
working_directory,
|
||||
argv,
|
||||
argv_buffer,
|
||||
argv_buffer_len,
|
||||
envp,
|
||||
close_descriptors,
|
||||
search_path,
|
||||
search_path_from_envp,
|
||||
chosen_search_path,
|
||||
search_path_buffer,
|
||||
search_path_buffer_len,
|
||||
stdout_to_null,
|
||||
stderr_to_null,
|
||||
child_inherits_stdin,
|
||||
@ -1853,10 +1959,13 @@ fork_exec_with_fds (gboolean intermediate_child,
|
||||
stderr_fd,
|
||||
working_directory,
|
||||
argv,
|
||||
argv_buffer,
|
||||
argv_buffer_len,
|
||||
envp,
|
||||
close_descriptors,
|
||||
search_path,
|
||||
search_path_from_envp,
|
||||
chosen_search_path,
|
||||
search_path_buffer,
|
||||
search_path_buffer_len,
|
||||
stdout_to_null,
|
||||
stderr_to_null,
|
||||
child_inherits_stdin,
|
||||
@ -1983,7 +2092,10 @@ fork_exec_with_fds (gboolean intermediate_child,
|
||||
/* Success against all odds! return the information */
|
||||
close_and_invalidate (&child_err_report_pipe[0]);
|
||||
close_and_invalidate (&child_pid_report_pipe[0]);
|
||||
|
||||
|
||||
g_free (search_path_buffer);
|
||||
g_free (argv_buffer);
|
||||
|
||||
if (child_pid)
|
||||
*child_pid = pid;
|
||||
|
||||
@ -2016,6 +2128,9 @@ fork_exec_with_fds (gboolean intermediate_child,
|
||||
close_and_invalidate (&child_pid_report_pipe[0]);
|
||||
close_and_invalidate (&child_pid_report_pipe[1]);
|
||||
|
||||
g_free (search_path_buffer);
|
||||
g_free (argv_buffer);
|
||||
|
||||
return FALSE;
|
||||
}
|
||||
|
||||
@ -2113,40 +2228,43 @@ cleanup_and_fail:
|
||||
|
||||
/* Based on execvp from GNU C Library */
|
||||
|
||||
static void
|
||||
/* This function is called between fork() and exec() and hence must be
|
||||
* async-signal-safe (see signal-safety(7)) until it calls exec(). */
|
||||
static gboolean
|
||||
script_execute (const gchar *file,
|
||||
gchar **argv,
|
||||
gchar **argv_buffer,
|
||||
gsize argv_buffer_len,
|
||||
gchar **envp)
|
||||
{
|
||||
/* Count the arguments. */
|
||||
int argc = 0;
|
||||
while (argv[argc])
|
||||
++argc;
|
||||
|
||||
/* Construct an argument list for the shell. */
|
||||
{
|
||||
gchar **new_argv;
|
||||
|
||||
new_argv = g_new0 (gchar*, argc + 2); /* /bin/sh and NULL */
|
||||
|
||||
new_argv[0] = (char *) "/bin/sh";
|
||||
new_argv[1] = (char *) file;
|
||||
while (argc > 0)
|
||||
{
|
||||
new_argv[argc + 1] = argv[argc];
|
||||
--argc;
|
||||
}
|
||||
/* Construct an argument list for the shell. */
|
||||
if (argc + 2 > argv_buffer_len)
|
||||
return FALSE;
|
||||
|
||||
/* Execute the shell. */
|
||||
if (envp)
|
||||
execve (new_argv[0], new_argv, envp);
|
||||
else
|
||||
execv (new_argv[0], new_argv);
|
||||
|
||||
g_free (new_argv);
|
||||
}
|
||||
argv_buffer[0] = (char *) "/bin/sh";
|
||||
argv_buffer[1] = (char *) file;
|
||||
while (argc > 0)
|
||||
{
|
||||
argv_buffer[argc + 1] = argv[argc];
|
||||
--argc;
|
||||
}
|
||||
|
||||
/* Execute the shell. */
|
||||
if (envp)
|
||||
execve (argv_buffer[0], argv_buffer, envp);
|
||||
else
|
||||
execv (argv_buffer[0], argv_buffer);
|
||||
|
||||
return TRUE;
|
||||
}
|
||||
|
||||
/* This function is called between fork() and exec() and hence must be
|
||||
* async-signal-safe (see signal-safety(7)). */
|
||||
static gchar*
|
||||
my_strchrnul (const gchar *str, gchar c)
|
||||
{
|
||||
@ -2157,12 +2275,17 @@ my_strchrnul (const gchar *str, gchar c)
|
||||
return p;
|
||||
}
|
||||
|
||||
/* This function is called between fork() and exec() and hence must be
|
||||
* async-signal-safe (see signal-safety(7)) until it calls exec(). */
|
||||
static gint
|
||||
g_execute (const gchar *file,
|
||||
gchar **argv,
|
||||
gchar **envp,
|
||||
gboolean search_path,
|
||||
gboolean search_path_from_envp)
|
||||
g_execute (const gchar *file,
|
||||
gchar **argv,
|
||||
gchar **argv_buffer,
|
||||
gsize argv_buffer_len,
|
||||
gchar **envp,
|
||||
const gchar *search_path,
|
||||
gchar *search_path_buffer,
|
||||
gsize search_path_buffer_len)
|
||||
{
|
||||
if (*file == '\0')
|
||||
{
|
||||
@ -2171,7 +2294,7 @@ g_execute (const gchar *file,
|
||||
return -1;
|
||||
}
|
||||
|
||||
if (!(search_path || search_path_from_envp) || strchr (file, '/') != NULL)
|
||||
if (search_path == NULL || strchr (file, '/') != NULL)
|
||||
{
|
||||
/* Don't search when it contains a slash. */
|
||||
if (envp)
|
||||
@ -2179,42 +2302,32 @@ g_execute (const gchar *file,
|
||||
else
|
||||
execv (file, argv);
|
||||
|
||||
if (errno == ENOEXEC)
|
||||
script_execute (file, argv, envp);
|
||||
if (errno == ENOEXEC &&
|
||||
!script_execute (file, argv, argv_buffer, argv_buffer_len, envp))
|
||||
{
|
||||
errno = ENOMEM;
|
||||
return -1;
|
||||
}
|
||||
}
|
||||
else
|
||||
{
|
||||
gboolean got_eacces = 0;
|
||||
const gchar *path, *p;
|
||||
gchar *name, *freeme;
|
||||
gchar *name;
|
||||
gsize len;
|
||||
gsize pathlen;
|
||||
|
||||
path = NULL;
|
||||
if (search_path_from_envp)
|
||||
path = g_environ_getenv (envp, "PATH");
|
||||
if (search_path && path == NULL)
|
||||
path = g_getenv ("PATH");
|
||||
|
||||
if (path == NULL)
|
||||
{
|
||||
/* There is no 'PATH' in the environment. The default
|
||||
* search path in libc is the current directory followed by
|
||||
* the path 'confstr' returns for '_CS_PATH'.
|
||||
*/
|
||||
|
||||
/* In GLib we put . last, for security, and don't use the
|
||||
* unportable confstr(); UNIX98 does not actually specify
|
||||
* what to search if PATH is unset. POSIX may, dunno.
|
||||
*/
|
||||
|
||||
path = "/bin:/usr/bin:.";
|
||||
}
|
||||
|
||||
path = search_path;
|
||||
len = strlen (file) + 1;
|
||||
pathlen = strlen (path);
|
||||
freeme = name = g_malloc (pathlen + len + 1);
|
||||
|
||||
name = search_path_buffer;
|
||||
|
||||
if (search_path_buffer_len < pathlen + len + 1)
|
||||
{
|
||||
errno = ENOMEM;
|
||||
return -1;
|
||||
}
|
||||
|
||||
/* Copy the file name at the top, including '\0' */
|
||||
memcpy (name + pathlen + 1, file, len);
|
||||
name = name + pathlen;
|
||||
@ -2243,8 +2356,12 @@ g_execute (const gchar *file,
|
||||
else
|
||||
execv (startp, argv);
|
||||
|
||||
if (errno == ENOEXEC)
|
||||
script_execute (startp, argv, envp);
|
||||
if (errno == ENOEXEC &&
|
||||
!script_execute (startp, argv, argv_buffer, argv_buffer_len, envp))
|
||||
{
|
||||
errno = ENOMEM;
|
||||
return -1;
|
||||
}
|
||||
|
||||
switch (errno)
|
||||
{
|
||||
@ -2282,7 +2399,6 @@ g_execute (const gchar *file,
|
||||
* something went wrong executing it; return the error to our
|
||||
* caller.
|
||||
*/
|
||||
g_free (freeme);
|
||||
return -1;
|
||||
}
|
||||
}
|
||||
@ -2294,8 +2410,6 @@ g_execute (const gchar *file,
|
||||
* error.
|
||||
*/
|
||||
errno = EACCES;
|
||||
|
||||
g_free (freeme);
|
||||
}
|
||||
|
||||
/* Return the error from the last attempt (probably ENOENT). */
|
||||
|
||||
Loading…
Reference in New Issue
Block a user