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Date: Mon, 1 Aug 2011 22:34:01 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: kernel-hardening@...ts.openwall.com
Cc: Ingo Molnar <mingo@...e.hu>,
"Paul E. McKenney" <paul.mckenney@...aro.org>,
Manuel Lauss <manuel.lauss@...glemail.com>,
linux-kernel@...r.kernel.org, Richard Weinberger <richard@....at>,
torvalds@...ux-foundation.org, Marc Zyngier <maz@...terjones.org>
Subject: Re: Re: initcall dependency problem (ns vs.
threads)
On Mon, Aug 01, 2011 at 11:20 -0700, Andrew Morton wrote:
> There's not really enough detail here for me to suggest a fix without
> actually doing some work. Which ipc initialization function is being
> called to late?
The call sequence is:
static int __init ipc_init(void)
{
...
shm_init();
...
}
__initcall(ipc_init);
void __init shm_init (void)
{
shm_init_ns(&init_ipc_ns);
...
void shm_init_ns(struct ipc_namespace *ns)
{
...
ipc_init_ids(&shm_ids(ns));
void ipc_init_ids(struct ipc_ids *ids)
{
init_rwsem(&ids->rw_mutex);
...
The code triggering the oops (called from do_exit()):
void exit_shm(struct task_struct *task)
{
...
down_write(&shm_ids(ns).rw_mutex);
> Which thread is using which data structures before
> which initialization function has been run?
Actually, it doesn't matter. If ANY thread exits before init_rwsem()
then exit_shm() would use uninitialized shm_ids(ns).rw_mutex.
> Are we talking about init_ipc_ns.ids[] here? If so, did you try
> initializing the three rwsems at compile-time?
No, good idea. I'll do it.
IMO moving specific initializer is bad by design. There should be a
guarantee what resources are accessible on what boot stage. I suppose
it should be: all thread related information (including ns data) is
accessible for the moment of threads' code execution.
Thanks,
--
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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