INIT_TASK() should initialize ->thread_group list
Oleg Nesterov [Wed, 26 May 2010 21:44:08 +0000 (14:44 -0700)]
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

index 0551e0d..6deb1ba 100644 (file)
@@ -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)                                           \