linux-kernel - Re: [PATCH 2/2] livepatch: fix patched module loading race

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Message-ID: <20150304224558.GE5464@treble.hsd1.ky.comcast.net>
Date:	Wed, 4 Mar 2015 16:45:58 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Petr Mladek <pmladek@...e.cz>, Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	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, andi@...stfloor.org,
	rostedt@...dmis.org, tglx@...utronix.de
Subject: Re: [PATCH 2/2] livepatch: fix patched module loading race

On Wed, Mar 04, 2015 at 11:02:59PM +0100, Jiri Kosina wrote:
> On Wed, 4 Mar 2015, Josh Poimboeuf wrote:
> 
> > Well, we could just get a reference on all patched modules to prevent them
> > from being unloaded.
> 
> Is that really a solution for cases where you are unloading a module (it 
> has "just" been switched to MODULE_STATE_GOING) and enable a patch which 
> patches one of its functions directly after it got switched to 
> MODULE_STATE_GOING?

Ah, right.  try_module_get() fails, we don't patch the module, and we
end up in the same mod->exit() race.  Never mind, again :-)

-- 
Josh
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