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gspawn: Use fdwalk provided by system only when it is known to be safe

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All uses of fdwalk in gspawn are between fork and exec, which means only
async-signal safe functions can be called if the parent process has
multiple threads. Since fdwalk is not a standard API, we should not
assume it is safe to use unless the manual of the system explicitly says
it is async-signal safe.

Fixes: #1638
This commit is contained in:
Ting-Wei Lan 2019-09-20 22:36:30 +08:00 committed by Philip Withnall
parent 2d37239510
commit 8af823c8e5
1 changed files with 17 additions and 5 deletions
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22
glib/gspawn.c
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@ -1148,7 +1148,6 @@ close_func (void *data, int fd)
return 0;
}
#ifndef HAVE_FDWALK
#ifdef __linux__
struct linux_dirent64
{
@ -1188,8 +1187,21 @@ filename_to_fd (const char *p)
#endif
static int
fdwalk (int (*cb)(void *data, int fd), void *data)
safe_fdwalk (int (*cb)(void *data, int fd), void *data)
{
#if 0
/* Use fdwalk function provided by the system if it is known to be
* async-signal safe.
*
* Currently there are no operating systems known to provide a safe
* implementation, so this section is not used for now.
*/
return fdwalk (cb, data);
#else
/* Fallback implementation of fdwalk. It should be async-signal safe, but it
* may be slow on non-Linux operating systems, especially on systems allowing
* very high number of open file descriptors.
*/
gint open_max;
gint fd;
gint res = 0;
@ -1244,8 +1256,8 @@ fdwalk (int (*cb)(void *data, int fd), void *data)
break;
return res;
#endif
}
#endif /* HAVE_FDWALK */
static void
safe_closefrom (int lowfd)
@ -1275,7 +1287,7 @@ safe_closefrom (int lowfd)
*/
(void) fcntl (lowfd, F_CLOSEM);
#else
(void) fdwalk (close_func, GINT_TO_POINTER (lowfd));
(void) safe_fdwalk (close_func, GINT_TO_POINTER (lowfd));
#endif
}
@ -1407,7 +1419,7 @@ do_exec (gint child_err_report_fd,
}
else
{
fdwalk (set_cloexec, GINT_TO_POINTER (3));
safe_fdwalk (set_cloexec, GINT_TO_POINTER (3));
}
}
else