linux-kernel - Re: [stable] [PATCH] modules fix incorrect percpu usage

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Message-ID: <20100420143457.GB14622@Krystal>
Date:	Tue, 20 Apr 2010 10:34:57 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Greg KH <greg@...ah.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Eric Dumazet <dada1@...mosbay.com>, Tejun Heo <tj@...nel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	stable <stable@...nel.org>
Subject: Re: [stable] [PATCH] modules fix incorrect percpu usage

* Greg KH (greg@...ah.com) wrote:
> On Tue, Mar 30, 2010 at 09:50:47AM -0400, Mathieu Desnoyers wrote:
> > * Steven Rostedt (rostedt@...dmis.org) wrote:
> > > On Mon, 2010-03-29 at 23:36 -0400, Mathieu Desnoyers wrote:
> > > > * Mathieu Desnoyers (mathieu.desnoyers@...icios.com) wrote:
> > > > > Should use per_cpu_ptr() to obfuscate the per cpu pointers (RELOC_HIDE is needed
> > > > > for per cpu pointers).
> > > > > 
> > > > > Introduced by commit:
> > > > > 
> > > > > module.c: commit 6b588c18f8dacfa6d7957c33c5ff832096e752d3
> > > > > 
> > > > > This patch should be queued for the stable branch, for kernels 2.6.29.x to
> > > > > 2.6.33.x.
> > > > > (tested on 2.6.33.1 x86_64)
> > > > 
> > > > It's actually needed for mainline too (2.6.34-rc2).
> > > 
> > > Then all you need to do is submit it for mainline with a 
> > > "Cc: stable@...nel.org" as you did below. It will then automatically be
> > > added to the stable queue when Linus pulls it.
> > 
> > OK, thanks for the info.
> 
> And I need to wait until it goes into Linus's tree before it can be
> applied to the stable tree.  This hasn't happened yet, right?
> 
> thanks,
> 
> greg k-h

Same here, for module.c fix. Feel free to choose between this fix or the
corresponding refactoring from Tejun.


modules fix incorrect percpu usage

Should use per_cpu_ptr() to obfuscate the per cpu pointers (RELOC_HIDE is needed
for per cpu pointers).

Introduced by commit:

module.c: commit 6b588c18f8dacfa6d7957c33c5ff832096e752d3

This patch should be queued for the stable branch, for kernels 2.6.29.x to
2.6.33.x.  (tested on 2.6.33.1 x86_64)

Mainline does not need this fix, as commit
259354deaaf03d49a02dbb9975d6ec2a54675672 fixed the problem by refactoring.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC: Randy Dunlap <randy.dunlap@...cle.com>
CC: Eric Dumazet <dada1@...mosbay.com>
CC: Rusty Russell <rusty@...tcorp.com.au>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC: Tejun Heo <tj@...nel.org>
CC: Ingo Molnar <mingo@...e.hu>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Greg Kroah-Hartman <gregkh@...e.de>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: stable <stable@...nel.org>
---
 kernel/module.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux.trees.git/kernel/module.c
===================================================================
--- linux.trees.git.orig/kernel/module.c	2010-03-27 11:27:23.000000000 -0400
+++ linux.trees.git/kernel/module.c	2010-03-30 09:48:41.000000000 -0400
@@ -405,7 +405,7 @@ static void percpu_modcopy(void *pcpudes
 	int cpu;
 
 	for_each_possible_cpu(cpu)
-		memcpy(pcpudest + per_cpu_offset(cpu), from, size);
+		memcpy(per_cpu_ptr(pcpudest, cpu), from, size);
 }
 
 #else /* ... !CONFIG_SMP */


-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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