linux-hardening - Re: [PATCH v2] x86/mm: Refuse W^X violations

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Message-ID: <08906193-246b-c874-8bac-1d98d2313ac4@roeck-us.net>
Date:   Thu, 22 Sep 2022 09:29:40 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        keescook@...omium.org, Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH v2] x86/mm: Refuse W^X violations

On 9/22/22 00:46, Peter Zijlstra wrote:
> On Wed, Sep 21, 2022 at 08:09:13PM -0700, Guenter Roeck wrote:
> 
>> Oh well, that "helped" to hide one of the crashes. Here is another one.
>> This is with PAE enabled and booting through efi32.
> 
>> [    1.086592]  efi_runtime_update_mappings+0x36/0x42
>> [    1.086717]  efi_enter_virtual_mode+0x351/0x36e
>> [    1.086860]  start_kernel+0x57d/0x60f
>> [    1.086956]  ? set_intr_gate+0x42/0x55
>> [    1.087079]  i386_start_kernel+0x43/0x45
>> [    1.087272]  startup_32_smp+0x161/0x164
> 
> Does this help? Dave; perhaps we should just let i386 be i386 and let it
> bitrot :/
> 
> diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
> index e06a199423c0..d81e379fcd43 100644
> --- a/arch/x86/platform/efi/efi_32.c
> +++ b/arch/x86/platform/efi/efi_32.c
> @@ -136,6 +136,7 @@ void __init efi_runtime_update_mappings(void)
>   			if (md->type != EFI_RUNTIME_SERVICES_CODE)
>   				continue;
>   
> +			set_memory_ro(md->virt_addr, md->num_pages);
>   			set_memory_x(md->virt_addr, md->num_pages);
>   		}
>   	}

Yes, it does.

Tested-by: Guenter Roeck <linux@...ck-us.net>

Guenter