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From: Oleg Nesterov on 10 May 2010 16:00
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(a)secunet.com>
Signed-off-by: Oleg Nesterov <oleg(a)redhat.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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