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

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Date:	Mon, 29 Nov 2010 11:59:04 -0500
From:	Valdis.Kletnieks@...edu
To:	mat <castet.matthieu@...e.fr>
Cc:	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>, Ingo Molnar <mingo@...e.hu>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Dave Jones <davej@...hat.com>,
	Siarhei Liakh <sliakh.lkml@...il.com>,
	Kees Cook <kees.cook@...onical.com>
Subject: Re: [PATCH 3/3 V13] RO/NX protection for loadable kernel

On Fri, 26 Nov 2010 18:23:55 +0100, mat said:

> Le Wed, 24 Nov 2010 22:41:07 -0500,
> Valdis.Kletnieks@...edu a =E9crit :

> > This is incompatible with CONFIG_JUMP_LABEL:
> >
> > [  252.093624] BUG: unable to handle kernel paging request at
> > ffffffffa0680764 [  252.094008] IP: [<ffffffff81225ee0>]
> > generic_swap+0xa/0x1a [  252.094008] PGD 1a1e067 PUD 1a22063 PMD
> > 1093ac067 PTE 8000000109786161 [  252.094008] Oops: 0003 [#1] PREEMPT
> > SMP

> > > +config DEBUG_SET_MODULE_RONX
> > > +	bool "Set loadable kernel module data as NX and text as RO"
> > > +	default n
> > > +	depends on X86 && MODULES
> >
> > 	depends on X86 && MODULES && !JUMP_LABEL
> could you try the attached patch ?
> 
> on module load, we sort the __jump_table section. So we should make it
> writable.

> diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_la
bel.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"\

Confirming that fixes the issue I was seeing, thanks...

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