linux-kernel - Re: [PATCH v14 04/11] livepatch: Refuse to unload only livepatches available during a forced transition

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Message-ID: <20181206084651.fvj5v4pdi4q2pigb@pathway.suse.cz>
Date:   Thu, 6 Dec 2018 09:46:51 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v14 04/11] livepatch: Refuse to unload only livepatches
 available during a forced transition

On Mon 2018-12-03 16:29:32, Miroslav Benes wrote:
> You probably forgot to replace the subject with Josh's proposal.
> 
> > module_put() is currently never called in klp_complete_transition() when
> > klp_force is set. As a result, we might keep the reference count even when
> > klp_enable_patch() fails and klp_cancel_transition() is called.
> 
> Correct.
> 
> > This might make an assumption that a module might get blocked in some
> > strange init state. Fortunately, it is not the case. The reference count
> > is ignored when mod->init fails and erroneous modules are always removed.
> 
> I do not understand the paragraph and its connection to the problem (and I don't
> remember if I understood it previously or not and forgot to mention it).

It was one example of the confusion. I wonder if the following text
is more clear:

One might wonder if the reference could block the module in
MODULE_STATE_COMING or MODULE_STATE_GOING infinitely.
Fortunately, it is not the case. The reference count is
ignored when mod->init fails and erroneous modules are
always removed.

Or I could remove the paragraph as you suggested below.


Best Regards,
Petr