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

From: Xiaotian Feng <xtfeng@gmail.com>
To: Valdis.Kletnieks@vt.edu
Cc: Ingo Molnar <mingo@elte.hu>, mat <castet.matthieu@free.fr>,
	Kees Cook <kees.cook@canonical.com>,
	linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-next@vger.kernel.org,
	Arjan van de Ven <arjan@infradead.org>,
	James Morris <jmorris@namei.org>,
	Andrew Morton <akpm@linux-foundation.org>, Andi Kleen <ak@muc.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Dave Jones <davej@redhat.com>,
	Siarhei Liakh <sliakh.lkml@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 3/3 V13] RO/NX protection for loadable kernel
Date: Fri, 7 Jan 2011 17:34:01 +0800	[thread overview]
Message-ID: <AANLkTin55DXcQnK3NY7y-v8TXj5w-XT2rTJo9p90tj4g@mail.gmail.com> (raw)
In-Reply-To: <34428.1293053719@localhost>

On Thu, Dec 23, 2010 at 5:35 AM,  <Valdis.Kletnieks@vt.edu> wrote:
> On Wed, 22 Dec 2010 13:40:19 +0100, Ingo Molnar said:
>>
>> * mat <castet.matthieu@free.fr> wrote:
>>
>> > Le Wed, 8 Dec 2010 14:19:51 -0800,
>> > Kees Cook <kees.cook@canonical.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@canonical.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.

Thanks
Xiaotian