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

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Date:	Tue, 11 May 2010 02:52:15 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Cedric Le Goater <clg@...t.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>,
	Sukadev Bhattiprolu <sukadev@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] INIT_TASK() should initialize ->thread_group list

Quoting Oleg Nesterov (oleg@...hat.com):
> 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>

Acked-by: Serge E. Hallyn <serue@...ibm.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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