From: Andy Lutomirski <luto@kernel.org>
Date: Fri, 15 Dec 2017 22:08:18 +0100
Subject: x86/mm/pti: Map ESPFIX into user space
Git-commit: 4b6bbe95b87966ba08999574db65c93c5e925a36
Patch-mainline: v4.15-rc6
References: bsc#1068032 CVE-2017-5754

Map the ESPFIX pages into user space when PTI is enabled.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/mm/pti.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 0e78797650a7..b1c38ef9fbbb 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -288,6 +288,16 @@ static void __init pti_clone_user_shared(void)
 }
 
 /*
+ * Clone the ESPFIX P4D into the user space visinble page table
+ */
+static void __init pti_setup_espfix64(void)
+{
+#ifdef CONFIG_X86_ESPFIX64
+	pti_clone_p4d(ESPFIX_BASE_ADDR);
+#endif
+}
+
+/*
  * Clone the populated PMDs of the entry and irqentry text and force it RO.
  */
 static void __init pti_clone_entry_text(void)
@@ -308,4 +318,5 @@ void __init pti_init(void)
 
 	pti_clone_user_shared();
 	pti_clone_entry_text();
+	pti_setup_espfix64();
 }