The code in forget_original_parent() that attempts to reparent a task to
another task in the thread group is broken. It's not safe to parent to any
task other than init because of the race condition it introduces (init is
only safe as long as it never dies, in fact).
The patch to change forget_original_parent() to always use init is below.
Dave McCracken
======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
[email protected] T/L 678-3059
---------------------
--- linux-2.4.12/kernel/exit.c Mon Sep 10 15:04:33 2001
+++ linux-2.4.12-signal-kdb/kernel/exit.c Thu Oct 18 11:31:57 2001
@@ -149,28 +149,21 @@
}
/*
- * When we die, we re-parent all our children.
- * Try to give them to another thread in our process
- * group, and if no such member exists, give it to
+ * When we die, we re-parent all our children to
* the global child reaper process (ie "init")
*/
static inline void forget_original_parent(struct task_struct * father)
{
- struct task_struct * p, *reaper;
+ struct task_struct * p;
read_lock(&tasklist_lock);
- /* Next in our thread group */
- reaper = next_thread(father);
- if (reaper == father)
- reaper = child_reaper;
-
for_each_task(p) {
if (p->p_opptr == father) {
/* We dont want people slaying init */
p->exit_signal = SIGCHLD;
p->self_exec_id++;
- p->p_opptr = reaper;
+ p->p_opptr = child_reaper;
if (p->pdeath_signal) send_sig(p->pdeath_signal, p, 0);
}
}
======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
[email protected] T/L 678-3059