[glib: 1/2] Handling collision between standard i/o file descriptors and newly created ones

[Marco Trevisan <marcotrevi src gnome org>]

commit d9ba6150909818beb05573f54f26232063492c5b
Author: Emmanuel Fleury <emmanuel fleury gmail com>
Date:   Mon Aug 1 19:05:14 2022 +0200

    Handling collision between standard i/o file descriptors and newly created ones
    
    Though unlikely to happen, it may happen that newly created file
    descriptor take the value 0 (stdin), 1 (stdout) or 2 (stderr) if one
    of the standard ones have been dismissed in between. So, it may
    confuse the program if it is unaware of this change.
    
    The point of this patch is to avoid a reasign of standard file
    descriptors on newly created ones.
    
    Closes issue #16

 glib/glib-unix.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
---
diff --git a/glib/glib-unix.c b/glib/glib-unix.c
index d2dea10ef0..d67b8a357a 100644
--- a/glib/glib-unix.c
+++ b/glib/glib-unix.c
@@ -108,6 +108,17 @@ g_unix_open_pipe (int     *fds,
     ecode = pipe2 (fds, pipe2_flags);
     if (ecode == -1 && errno != ENOSYS)
       return g_unix_set_error_from_errno (error, errno);
+    /* Don't reassign pipes to stdin, stdout, stderr if closed meanwhile */
+    else if (fds[0] < 3 || fds[1] < 3)
+      {
+        int old_fds[2] = { fds[0], fds[1] };
+        gboolean result = g_unix_open_pipe (fds, flags, error);
+        close (old_fds[0]);
+        close (old_fds[1]);
+
+        if (!result)
+          g_unix_set_error_from_errno (error, errno);
+      }
     else if (ecode == 0)
       return TRUE;
     /* Fall through on -ENOSYS, we must be running on an old kernel */
@@ -116,6 +127,19 @@ g_unix_open_pipe (int     *fds,
   ecode = pipe (fds);
   if (ecode == -1)
     return g_unix_set_error_from_errno (error, errno);
+  /* Don't reassign pipes to stdin, stdout, stderr if closed meanwhile */
+  else if (fds[0] < 3 || fds[1] < 3)
+    {
+      int old_fds[2] = { fds[0], fds[1] };
+      gboolean result = g_unix_open_pipe (fds, flags, error);
+      close (old_fds[0]);
+      close (old_fds[1]);
+
+      if (!result)
+        g_unix_set_error_from_errno (error, errno);
+
+      return result;
+    }
 
   if (flags == 0)
     return TRUE;