linux-kernel - Re: [PATCH 3/3 V13] RO/NX protection for loadable kernel

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Date:	Thu, 20 Jan 2011 21:32:00 +0100
From:	matthieu castet <castet.matthieu@...e.fr>
To:	Xiaotian Feng <xtfeng@...il.com>
CC:	Valdis.Kletnieks@...edu, Ingo Molnar <mingo@...e.hu>,
	Kees Cook <kees.cook@...onical.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-next@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Dave Jones <davej@...hat.com>,
	Siarhei Liakh <sliakh.lkml@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 3/3 V13] RO/NX protection for loadable kernel

Xiaotian Feng a écrit :
> On Thu, Dec 23, 2010 at 5:35 AM,  <Valdis.Kletnieks@...edu> wrote:
>> On Wed, 22 Dec 2010 13:40:19 +0100, Ingo Molnar said:
>>> * mat <castet.matthieu@...e.fr> wrote:
>>>
>>>> Le Wed, 8 Dec 2010 14:19:51 -0800,
>>>> Kees Cook <kees.cook@...onical.com> a écrit :
>>>>
>>>>> On Fri, Nov 26, 2010 at 06:23:55PM +0100, mat wrote:
>>>>>> could you try the attached patch ?
>>>>>>
>>>>>> on module load, we sort the __jump_table section. So we should make
>>>>>> it writable.
>>>>>>
>>>>>>
>>>>>> Matthieu
>>>>>> diff --git a/arch/x86/include/asm/jump_label.h
>>>>>> b/arch/x86/include/asm/jump_label.h index f52d42e..574dbc2 100644
>>>>>> --- a/arch/x86/include/asm/jump_label.h
>>>>>> +++ b/arch/x86/include/asm/jump_label.h
>>>>>> @@ -14,7 +14,7 @@
>>>>>>         do
>>>>>> {                                                       \ asm
>>>>>> goto("1:"                                       \
>>>>>> JUMP_LABEL_INITIAL_NOP                  \
>>>>>> -                       ".pushsection __jump_table,  \"a\" \n\t"\
>>>>>> +                       ".pushsection __jump_table,  \"aw\" \n\t"\
>>>>>>                         _ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
>>>>>>                         ".popsection \n\t"                      \
>>>>>>                         : :  "i" (key) :  : label);
>>>>>> \
>>>>> Acked-by: Kees Cook <kees.cook@...onical.com>
>>>>>
>>>>> Can this please get committed to tip?
>>>> I think it is not need anymore with  Steven Rostedt patch [1]
>>>>
>>>> Matthieu
>>>>
>>>> [1]
>>>>>> Here we set the text read only before we call the notifiers. The
>>>>>> function tracer changes the calls to mcount into nops via a notifier
>>>>>> call so this must be done after the module notifiers.
>>> What's the status of this bug?
>>>
>>> If we still need the patch then please submit it standalone with a proper subject
>>> line, with acks/signoffs added, etc.
>> Steve Rostedt's patch that moves the setting of the page permissions seems to
>> make this patch no longer necessary.  I tripped over this same issue, but the
>> version in the latest -mmotm does not need it, as it includes Steve's fix.
>>
> 
> I'm facing a boot failure (panic'ed on remove_jump_label_module_init)
> on 2.6.37 (latest commit 3c0cb7c), which is 100% reproducible.
> With this patch applied, I can boot my machine successfully, so I do
> think this patch is needed.
> 
Could you confirm that this patch fix the problem ?


Matthieu

View attachment "0001-Fix-jump-table-in-module-init-section.patch" of type "text/x-diff" (1146 bytes)