[glib/mcatanzaro/posix-spawn2: 16/18] gspawn: fix hangs when duping child_err_report_fd

[Michael Catanzaro <mcatanzaro src gnome org>]

commit c026c443906a3846a7dba588f9a80414eb5a5e87
Author: Michael Catanzaro <mcatanzaro redhat com>
Date:   Tue Oct 12 15:33:59 2021 -0500

    gspawn: fix hangs when duping child_err_report_fd
    
    In case child_err_report_fd conflicts with one of the target_fds, the
    code here is careful to dup child_err_report_fd in order to avoid
    conflating the two. It was a good idea, but evidently was not tested,
    because the newly-created fd is not created with CLOEXEC set. This means
    it stays open in the child process, causing the parent to hang forever
    waiting to read from the other end of the pipe. Oops!
    
    The fix is simple: just set CLOEXEC. This removes our only usage of the
    safe_dup() function, so it can be dropped.

 glib/gspawn.c | 16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)
---
diff --git a/glib/gspawn.c b/glib/gspawn.c
index 2b191634c..a889ab0bf 100644
--- a/glib/gspawn.c
+++ b/glib/gspawn.c
@@ -1588,20 +1588,6 @@ safe_closefrom (int lowfd)
 #endif
 }
 
-/* This function is called between fork() and exec() and hence must be
- * async-signal-safe (see signal-safety(7)). */
-static gint
-safe_dup (gint fd)
-{
-  gint ret;
-
-  do
-    ret = dup (fd);
-  while (ret < 0 && (errno == EINTR || errno == EBUSY));
-
-  return ret;
-}
-
 /* This function is called between fork() and exec() and hence must be
  * async-signal-safe (see signal-safety(7)). */
 static gint
@@ -1795,7 +1781,7 @@ do_exec (gint                  child_err_report_fd,
           else
             {
               if (target_fds[i] == child_err_report_fd)
-                child_err_report_fd = safe_dup (child_err_report_fd);
+                child_err_report_fd = dupfd_cloexec (child_err_report_fd);
 
               safe_dup2 (source_fds[i], target_fds[i]);
               close_and_invalidate (&source_fds[i]);