A patch for the file kernel/fork.c

["André Pereira de Almeida" <andre@cachola.com.br>]

  I think that the file kernel/fork.c should be patched as following:

--- linux-2.6.12-rc3.orig/kernel/fork.c 2005-05-03 22:31:21.000000000 -0300
+++ linux-2.6.12-rc3/kernel/fork.c      2005-05-04 09:37:46.000000000 -0300
@@ -429,7 +429,7 @@
                tsk->vfork_done = NULL;
                complete(vfork_done);
        }
-       if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
+       if (mm && tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
                u32 __user * tidptr = tsk->clear_child_tid;
                tsk->clear_child_tid = NULL;

If a process is killed and, for some reason, when closing all files a 
pagefault is generated (should not happen, but...) after the function 
exit_mm had been called, the kernel will try to exit this process again, 
calling exit_mm and mm_release with a null mm, and will generate another 
pagefault in atomic_read(&mm->mm_users), and so on and the system will 
hang. I think this patch solve this problem.