linux-kernel - Re: [PATCH v4] livepatch/module: Correctly handle coming and going modules

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Message-ID: <873854mluc.fsf@rustcorp.com.au>
Date:	Tue, 17 Mar 2015 12:22:43 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jiri Kosina <jkosina@...e.cz>, Petr Mladek <pmladek@...e.cz>
Cc:	Seth Jennings <sjenning@...hat.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	mingo@...nel.org, mathieu.desnoyers@...icios.com, oleg@...hat.com,
	paulmck@...ux.vnet.ibm.com, live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org, andi@...stfloor.org,
	rostedt@...dmis.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v4] livepatch/module: Correctly handle coming and going modules

Jiri Kosina <jkosina@...e.cz> writes:
> On Thu, 12 Mar 2015, Petr Mladek wrote:
>
>> There is a notifier that handles live patches for coming and going modules.
>> It takes klp_mutex lock to avoid races with coming and going patches but
>> it does not keep the lock all the time. Therefore the following races are
>> possible:
> [ ... snip ... ]
>> diff --git a/include/linux/module.h b/include/linux/module.h
>> index b653d7c0a05a..7232fde6a991 100644
>> --- a/include/linux/module.h
>> +++ b/include/linux/module.h
>> @@ -344,6 +344,10 @@ struct module {
>>  	unsigned long *ftrace_callsites;
>>  #endif
>>  
>> +#ifdef CONFIG_LIVEPATCH
>> +	bool klp_alive;
>> +#endif
>> +
>
> Rusty, are you okay with this please? I'd like to have the race fixed in 
> 4.0 still, but don't want to be making changes to struct module without 
> your ack.

I look at the amount of explanation and discussion around these patches
and I fear the complexity of what you're doing.

But not enough to rewrite it myself, so:

Acked-by: Rusty Russell <rusty@...tcorp.com.au>

Good luck!
Rusty.
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