linux-kernel - Re: [PATCH] module: fix refptr allocation and release order

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Message-Id: <200903180751.55665.rusty@rustcorp.com.au>
Date:	Wed, 18 Mar 2009 07:51:55 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"systemtap-ml" <systemtap@...rces.redhat.com>
Subject: Re: [PATCH] module: fix refptr allocation and release order

On Tuesday 17 March 2009 13:54:36 Eric Dumazet wrote:
> Rusty Russell a écrit :
> > From: Masami Hiramatsu <mhiramat@...hat.com>
> > 
> > Impact: fix ref-after-free crash on failed module load
> > 
> > Fix refptr bug: Change refptr allocation and release order not to access a module
> > data structure pointed by 'mod' after freeing mod->module_core.
> > This bug will cause kernel panic(e.g. failed to find undefined symbols).
> > 
> > This bug was reported on systemtap bugzilla.
> > http://sources.redhat.com/bugzilla/show_bug.cgi?id=9927
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
> > Cc: Eric Dumazet <dada1@...mosbay.com>
> > Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> 
> 
> My original patch did not have this problem, because I used a local variable
> to hold refptr.
> 
> http://www.archivum.info/linux-kernel@vger.kernel.org/2008-05/msg07400.html
> 
> A simpler patch could just use a local variable again, since we are very
> late in rc phase ?

Right, it was my mistake.  But the extra #ifdef is still ugly: moving the code
is a larger patch, but it's not complicated.

Thanks,
Rusty.
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