From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Miroslav Benes <mbenes@suse.cz>
Cc: Jiri Kosina <jikos@kernel.org>,
jeyu@redhat.com, pmladek@suse.com, jslaby@suse.cz,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
huawei.libin@huawei.com, minfei.huang@yahoo.com
Subject: Re: [RFC PATCH] livepatch: allow removal of a disabled patch
Date: Thu, 5 May 2016 08:27:48 -0500 [thread overview]
Message-ID: <20160505132748.kwk3pmgetud3c66r@treble> (raw)
In-Reply-To: <alpine.LNX.2.00.1605051008240.19692@pobox.suse.cz>
On Thu, May 05, 2016 at 10:28:12AM +0200, Miroslav Benes wrote:
> I think it boils down to the following problem.
>
> 1. CONFIG_DEBUG_KOBJECT_RELEASE=y
>
> 2. we have dynamic kobjects, so there is a pointer in klp_patch to struct
> kobject
>
> 3. it is allocated during klp_init_patch() and all is fine
>
> 4. now we want to remove the patch module. It is disabled and module_put()
> is called. User calls rmmod on the module.
>
> 5. klp_unregister_patch() is called in __exit method.
>
> 6. klp_free_patch() is called.
>
> 7. kobject_put(patch->kobj) is called.
>
> ...now it gets interesting...
>
> 8. among others kobject_cleanup() is scheduled as a delayed work (this is
> important).
>
> 9. there is no completion, so kobject_put returns and the module goes
> away.
>
> 10. someone calls patch enabled_store attribute (for example). They can
> because kobject_cleanup() has not been called yet. It is delayed
> scheduled.
>
> ...crash...
But what exactly causes the crash? In enabled_store() we can see that
the patch isn't in the list, so we can return -EINVAL.
--
Josh
next prev parent reply other threads:[~2016-05-05 13:27 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-02 11:57 [RFC PATCH] livepatch: allow removal of a disabled patch Miroslav Benes
2016-05-02 15:08 ` Josh Poimboeuf
2016-05-03 8:16 ` Miroslav Benes
2016-05-31 23:13 ` Jiri Kosina
2016-05-03 21:37 ` Josh Poimboeuf
2016-05-03 22:31 ` Jiri Kosina
2016-05-04 2:39 ` Josh Poimboeuf
2016-05-04 3:36 ` Josh Poimboeuf
2016-05-04 11:58 ` Miroslav Benes
2016-05-04 13:14 ` Josh Poimboeuf
2016-05-04 14:35 ` Miroslav Benes
2016-05-04 16:14 ` Josh Poimboeuf
2016-05-05 8:28 ` Miroslav Benes
2016-05-05 13:27 ` Josh Poimboeuf [this message]
2016-05-05 14:25 ` Miroslav Benes
2016-05-05 15:04 ` Josh Poimboeuf
2016-05-05 21:08 ` Jiri Kosina
2016-05-06 0:42 ` Jessica Yu
2016-05-06 7:51 ` Miroslav Benes
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