linux-kernel - Re: [PATCH] xen: do not set NX bit when making initial pagetables readonly

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <1233341449.7436.4.camel@localhost.localdomain>
Date:	Fri, 30 Jan 2009 18:50:49 +0000
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Mark McLoughlin <markmc@...hat.com>
Cc:	Jon Swanson <jswanson@...uecommerce.co.jp>, fedora-virt@...hat.com,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	stable@...nel.org
Subject: Re: [PATCH] xen: do not set NX bit when making initial pagetables
	readonly

I meant to CC lkml and stable@ (some of the original reports are against
2.6.27) and fat-fingered the to: line.

A few previous threads on the subject:
http://lists.xensource.com/archives/html/xen-devel/2009-01/msg00176.html
http://www.redhat.com/archives/fedora-xen/2009-January/msg00022.html
http://www.redhat.com/archives/fedora-virt/2009-January/msg00013.html

Ian.

On Fri, 2009-01-30 at 18:19 +0000, Ian Campbell wrote:
> __supported_pte_mask has not been correctly configured at this point
> and Xen prevents us from using the NX bit if the hardware does not
> support it. Some BIOSes seem to offer the option to disable NX.
> 
> Signed-off-by: Ian Campbell <ian.campbell@...rix.com>
> Cc: Mark McLoughlin <markmc@...hat.com>
> Cc: Jon Swanson <jswanson@...uecommerce.co.jp>
> Cc: fedora-virt@...hat.com
> Cc: Jeremy Fitzhardinge <jeremy@...p.org>
> Cc: Ingo Molnar <mingo@...e.hu>
> ---
>  arch/x86/xen/enlighten.c |   24 +++++++++++++-----------
>  1 files changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index bea2152..e705bdf 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -53,6 +53,8 @@
>  #include "mmu.h"
>  #include "multicalls.h"
>  
> +#define _KERNPG_TABLE_RO __pgprot(_KERNPG_TABLE & ~_PAGE_RW)
> +
>  EXPORT_SYMBOL_GPL(hypercall_page);
>  
>  DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
> @@ -1487,9 +1489,9 @@ static __init void xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
>  	}
>  
>  	for (pteidx = 0; pteidx < ident_pte; pteidx += PTRS_PER_PTE)
> -		set_page_prot(&level1_ident_pgt[pteidx], PAGE_KERNEL_RO);
> +		set_page_prot(&level1_ident_pgt[pteidx], _KERNPG_TABLE_RO);
>  
> -	set_page_prot(pmd, PAGE_KERNEL_RO);
> +	set_page_prot(pmd, _KERNPG_TABLE_RO);
>  }
>  
>  #ifdef CONFIG_X86_64
> @@ -1543,12 +1545,12 @@ static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
>  	xen_map_identity_early(level2_ident_pgt, max_pfn);
>  
>  	/* Make pagetable pieces RO */
> -	set_page_prot(init_level4_pgt, PAGE_KERNEL_RO);
> -	set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
> -	set_page_prot(level3_kernel_pgt, PAGE_KERNEL_RO);
> -	set_page_prot(level3_user_vsyscall, PAGE_KERNEL_RO);
> -	set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
> -	set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
> +	set_page_prot(init_level4_pgt, _KERNPG_TABLE_RO);
> +	set_page_prot(level3_ident_pgt, _KERNPG_TABLE_RO);
> +	set_page_prot(level3_kernel_pgt, _KERNPG_TABLE_RO);
> +	set_page_prot(level3_user_vsyscall, _KERNPG_TABLE_RO);
> +	set_page_prot(level2_kernel_pgt, _KERNPG_TABLE_RO);
> +	set_page_prot(level2_fixmap_pgt, _KERNPG_TABLE_RO);
>  
>  	/* Pin down new L4 */
>  	pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
> @@ -1597,9 +1599,9 @@ static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
>  	set_pgd(&swapper_pg_dir[KERNEL_PGD_BOUNDARY],
>  			__pgd(__pa(level2_kernel_pgt) | _PAGE_PRESENT));
>  
> -	set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
> -	set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
> -	set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
> +	set_page_prot(level2_kernel_pgt, _KERNPG_TABLE_RO);
> +	set_page_prot(swapper_pg_dir, _KERNPG_TABLE_RO);
> +	set_page_prot(empty_zero_page, _KERNPG_TABLE_RO);
>  
>  	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
>  

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/