[glib/th/gspawn-no-safe-close: 4/4] gspawn: avoid race due to retry with EINTR on close()

[Thomas Haller <thaller src gnome org>]

commit afa66d58934f28017e09487bd3d382ce1b273ff4
Author: Thomas Haller <thaller redhat com>
Date:   Wed Oct 12 23:30:37 2022 +0200

    gspawn: avoid race due to retry with EINTR on close()
    
    Retry on EINTR is wrong on many OS, including Linux. See the comment
    in _g_safe_close_with_error() why that is.
    
    As we cannot use g_close() after fork, we had safe_close(). This had the
    wrong retry loop on EINTR. Drop that.
    
    This was especially problematic since commit 6f46294227f8 ('gspawn: Don’t
    use g_close() in async-signal-safe context'). Before, safe_close() was
    only called after fork, where there is only one thread and there is no
    concern about a race.
    
    Replace safe_close() with _g_safe_close() which gets all the things
    right, including the (not) handling of EINTR, the ignoring of any other
    error, being async-signal-safe (aside assertion failures for EBADF).
    
    Fixes: 6f46294227f8 ('gspawn: Don’t use g_close() in async-signal-safe context')

 glib/gspawn.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)
---
diff --git a/glib/gspawn.c b/glib/gspawn.c
index 4e029eedf5..b748cc9fe5 100644
--- a/glib/gspawn.c
+++ b/glib/gspawn.c
@@ -58,6 +58,7 @@
 #include "gthread.h"
 #include "gtrace-private.h"
 #include "glib/gstdio.h"
+#include "gutilsprivate.h"
 
 #include "genviron.h"
 #include "gmem.h"
@@ -162,8 +163,6 @@ extern char **environ;
  */
 
 
-static gint safe_close (gint fd);
-
 static gint g_execute (const gchar  *file,
                        gchar       **argv,
                        gchar       **argv_buffer,
@@ -267,11 +266,9 @@ close_and_invalidate (gint *fd)
 {
   if (*fd < 0)
     return;
-  else
-    {
-      safe_close (*fd);
-      *fd = -1;
-    }
+
+  _g_safe_close (*fd);
+  *fd = -1;
 }
 
 /* Some versions of OS X define READ_OK in public headers */
@@ -1338,27 +1335,13 @@ dupfd_cloexec (int old_fd, int new_fd_min)
   return fd;
 }
 
-/* This function is called between fork() and exec() and hence must be
- * async-signal-safe (see signal-safety(7)). */
-static gint
-safe_close (gint fd)
-{
-  gint ret;
-
-  do
-    ret = close (fd);
-  while (ret < 0 && errno == EINTR);
-
-  return ret;
-}
-
 /* This function is called between fork() and exec() and hence must be
  * async-signal-safe (see signal-safety(7)). */
 G_GNUC_UNUSED static int
 close_func (void *data, int fd)
 {
   if (fd >= GPOINTER_TO_INT (data))
-    (void) safe_close (fd);
+    _g_safe_close (fd);
 
   return 0;
 }
@@ -1453,7 +1436,7 @@ safe_fdwalk (int (*cb)(void *data, int fd), void *data)
             }
         }
 
-      safe_close (dir_fd);
+      _g_safe_close (dir_fd);
       return res;
     }