From fa2755e20ab0c7215d99c2dc7c262e98a09b01df Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 26 May 2010 14:44:08 -0700
Subject: [PATCH] INIT_TASK() should initialize ->thread_group list

The trivial /sbin/init doing

	int main(void)
	{
		kill(0, SIGKILL)
	}

crashes the kernel.

This happens because __kill_pgrp_info(init_struct_pid) also sends SIGKILL
to the swapper process which runs with the uninitialized ->thread_group.

Change INIT_TASK() to initialize ->thread_group properly.

Note: the real problem is that the swapper process must not be visible to
signals, see the next patch. But this change is right anyway and fixes
the crash.

Reported-and-tested-by: Mathias Krause <mathias.krause@secunet.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Mathias Krause <Mathias.Krause@secunet.com>
Acked-by: Roland McGrath <roland@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 include/linux/init_task.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 0551e0dcb71..6deb1ba52fd 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -163,6 +163,7 @@ extern struct cred init_cred;
 		[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID),		\
 		[PIDTYPE_SID]  = INIT_PID_LINK(PIDTYPE_SID),		\
 	},								\
+	.thread_group	= LIST_HEAD_INIT(tsk.thread_group),		\
 	.dirties = INIT_PROP_LOCAL_SINGLE(dirties),			\
 	INIT_IDS							\
 	INIT_PERF_EVENTS(tsk)						\
-- 
2.39.2