linux-kernel - [PATCH 1/4] INIT_TASK() should initialize ->thread

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Date:	Mon, 10 May 2010 21:49:49 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Cedric Le Goater <clg@...ibm.com>,
	Dave Hansen <haveblue@...ibm.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Ingo Molnar <mingo@...e.hu>,
	Mathias Krause <Mathias.Krause@...unet.com>,
	Roland McGrath <roland@...hat.com>,
	Serge Hallyn <serue@...ibm.com>,
	Sukadev Bhattiprolu <sukadev@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] 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@...unet.com>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---

 include/linux/init_task.h |    1 +
 1 file changed, 1 insertion(+)

--- 34-rc1/include/linux/init_task.h~1_INIT_TASK_THREAD_GROUP	2010-05-10 19:44:19.000000000 +0200
+++ 34-rc1/include/linux/init_task.h	2010-05-10 19:45:27.000000000 +0200
@@ -172,6 +172,7 @@ 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)						\

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