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 <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Cc: Cedric Le Goater <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Herbert Poetzl <[email protected]>
Cc: Mathias Krause <[email protected]>
Acked-by: Roland McGrath <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Acked-by: Sukadev Bhattiprolu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 0551e0dcb71b70072f09e887fb56feea85d77276..6deb1ba52fdb69f37097ef7bf5c80d8fe54c507d 100644 (file)
--- 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)                                           \