[BUG 2.4.6] PPID of a process is set to itself

[Tachino Nobuhiro <tachino@open.nm.fujitsu.co.jp>]

Hi,

When I am playing with clone system call, I found the case the cloned process
becomes the zombie which is not reaped because the PPID of the process is
set to itself. The test program are following.



#include <sched.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

int	stack[2048];

int
func(void *p)
{
	exit(0);
}

int
main(int argc, char *argv[])
{
	clone(func, &stack[2048],
		CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD,
		NULL);

	sleep(1);
	exit(0);
}

Following patch fixes the bug, but I don't know this is correct. Can
someone please explain me why in forget_original_parent(), the parent of
processes in a thread group is set to another process in the thread
group?

diff -u -r linux.org/kernel/exit.c linux/kernel/exit.c
--- linux.org/kernel/exit.c	Sat May  5 06:44:06 2001
+++ linux/kernel/exit.c	Tue Jul 17 11:06:59 2001
@@ -168,7 +168,7 @@
 			/* We dont want people slaying init */
 			p->exit_signal = SIGCHLD;
 			p->self_exec_id++;
-			p->p_opptr = reaper;
+			p->p_opptr = p == reaper ? child_reaper : reaper;
 			if (p->pdeath_signal) send_sig(p->pdeath_signal, p, 0);
 		}
 	}