Bug 145173

Can you reproduce it in version 4.23? I don't have accelerated card in beta3 to test it.

It is disabled by default, so decreasing to normal. If this will cause problems, we can remove this module at all.

yes, it's reproducible with 4.23
no, you don't need GL support to test it

and it's critical as it's creating a DoS - you can't login back into the machine as the kernel won't allow new processes to be started and you need to reset.

glslideshow removed. Mail was sent to author (JWZ). We can re-test the module later and re-enable it.

From: Jamie Zawinski
To: Stanislav Brabec
Subject: Re: xscreensaver: zombie  DoS from glslideshow
Date: Sun, 19 Mar 2006 17:38:06 -0800

I think this should fix it -- let me know?

RCS file: /cvsroot/xscreensaver/utils/grabclient.c,v
retrieving revision 1.17
diff -u -r1.17 grabclient.c
--- grabclient.c        1 Mar 2006 11:35:52 -0000       1.17
+++ grabclient.c        20 Mar 2006 01:35:43 -0000
@@ -302,6 +302,7 @@
    FILE *read_pipe;
    FILE *write_pipe;
    XtInputId pipe_id;
+  pid_t pid;
} grabclient_data;
@@ -350,7 +351,8 @@
                     (XtPointer) (XtInputReadMask | XtInputExceptMask),
                     finalize_cb, (XtPointer) data);
-  switch ((int) (forked = fork ()))
+  forked = fork ();
+  switch ((int) forked)
      {
      case -1:
        sprintf (buf, "%s: couldn't fork", progname);
@@ -379,6 +381,7 @@
      default:                                  /* parent */
        fclose (data->write_pipe);
        data->write_pipe = 0;
+      data->pid = forked;
        break;
      }
}
@@ -405,6 +408,14 @@
    if (name) free (name);
    fclose (data->read_pipe);
+
+  if (data->pid)       /* reap zombies */
+    {
+      int status;
+      waitpid (data->pid, &status, 0);
+      data->pid = 0;
+    }
+
    memset (data, 0, sizeof (*data));
    free (data);
}


--
Jamie Zawinski ...

From: Stanislav Brabec
To: Jamie Zawinski
Subject: Re: xscreensaver: zombie  DoS from glslideshow
Date: Tue, 21 Mar 2006 17:27:09 +0100

Jamie Zawinski writes:
> I think this should fix it -- let me know?

The patch looks somehow mangled, but after backporting it to 4.23
(attached) it seems not to fix this problem.

--- grabclient.c
+++ grabclient.c
@@ -303,6 +303,7 @@
   FILE *read_pipe;
   FILE *write_pipe;
   XtInputId pipe_id;
+  pid_t pid;
 } grabclient_data;
 
 
@@ -350,7 +351,8 @@
                    (XtPointer) (XtInputReadMask | XtInputExceptMask),
                    finalize_cb, (XtPointer) data);
 
-  switch ((int) (forked = fork ()))
+  forked = fork ();
+  switch ((int) forked)
     {
     case -1:
       sprintf (buf, "%s: couldn't fork", progname);
@@ -361,6 +363,7 @@
 
       fclose (data->read_pipe);
       data->read_pipe = 0;
+      data->pid = forked;
 
       /* clone the write pipe onto stdout so that it gets closed
          when the fork exits.  This will shut down the pipe and
@@ -405,6 +408,14 @@
   if (name) free (name);
 
   fclose (data->read_pipe);
+
+  if (data->pid)       /* reap zombies */
+  {
+      int status;
+      waitpid (data->pid, &status, 0);
+      data->pid = 0;
+  }
+
   memset (data, 0, sizeof (*data));
   free (data);
 }

Is glsideshow coming back?  It is not in my up2dated 10.1.

Brian

No. Patch from Jamie Zawinski did not fix the zombie DoS.

Fixed in xscreensaver-5.01 (even reporter can't reproduce it any more)