pve-edge-kernel/patches/kernel/0254-x86-tboot-Unbreak-tboot-with-PTI-enabled.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Dave Hansen <[email protected]>
Date: Sat, 6 Jan 2018 18:41:14 +0100
Subject: [PATCH] x86/tboot: Unbreak tboot with PTI enabled
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CVE-2017-5754

This is another case similar to what EFI does: create a new set of
page tables, map some code at a low address, and jump to it.  PTI
mistakes this low address for userspace and mistakenly marks it
non-executable in an effort to make it unusable for userspace.

Undo the poison to allow execution.

Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig")
Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Andrea Arcangeli <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Alan Cox <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Jon Masters <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Jeff Law <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: David" <[email protected]>
Cc: Nick Clifton <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
(cherry picked from commit 262b6b30087246abf09d6275eb0c0dc421bcbe38)
Signed-off-by: Andy Whitcroft <[email protected]>
Signed-off-by: Kleber Sacilotto de Souza <[email protected]>
(cherry picked from commit f03e9108405491791f0b883a2d95e2620ddfce64)
Signed-off-by: Fabian Grünbichler <[email protected]>
---
 arch/x86/kernel/tboot.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index a4eb27918ceb..75869a4b6c41 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -127,6 +127,7 @@ static int map_tboot_page(unsigned long vaddr, unsigned long pfn,
 	p4d = p4d_alloc(&tboot_mm, pgd, vaddr);
 	if (!p4d)
 		return -1;
+	pgd->pgd &= ~_PAGE_NX;
 	pud = pud_alloc(&tboot_mm, p4d, vaddr);
 	if (!pud)
 		return -1;
-- 
2.14.2