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

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Message-ID: <YywS0keUorHwJJPt@hirez.programming.kicks-ass.net>
Date:   Thu, 22 Sep 2022 09:46:26 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Guenter Roeck <linux@...ck-us.net>
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 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);
 		}
 	}