pve-edge-kernel/patches/kernel/0092-x86-entry-64-Simplify-reg-restore-code-in-the-standa.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <[email protected]>
Date: Thu, 2 Nov 2017 00:59:01 -0700
Subject: [PATCH] x86/entry/64: Simplify reg restore code in the standard IRET
 paths
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CVE-2017-5754

The old code restored all the registers with movq instead of pop.

In theory, this was done because some CPUs have higher movq
throughput, but any gain there would be tiny and is almost certainly
outweighed by the higher text size.

This saves 96 bytes of text.

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/ad82520a207ccd851b04ba613f4f752b33ac05f7.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>
(cherry picked from commit e872045bfd9c465a8555bab4b8567d56a4d2d3bb)
Signed-off-by: Andy Whitcroft <[email protected]>
Signed-off-by: Kleber Sacilotto de Souza <[email protected]>
(cherry picked from commit f926575cd370de4052e89477582b349af5664a56)
Signed-off-by: Fabian Grünbichler <[email protected]>
---
 arch/x86/entry/calling.h  | 21 +++++++++++++++++++++
 arch/x86/entry/entry_64.S | 12 ++++++------
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 640aafebdc00..0b9dd8123701 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -151,6 +151,27 @@ For 32-bit we have the following conventions - kernel is built with
 	UNWIND_HINT_REGS offset=\offset extra=0
 	.endm
 
+	.macro POP_EXTRA_REGS
+	popq %r15
+	popq %r14
+	popq %r13
+	popq %r12
+	popq %rbp
+	popq %rbx
+	.endm
+
+	.macro POP_C_REGS
+	popq %r11
+	popq %r10
+	popq %r9
+	popq %r8
+	popq %rax
+	popq %rcx
+	popq %rdx
+	popq %rsi
+	popq %rdi
+	.endm
+
 	.macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
 	.if \rstor_r11
 	movq 6*8(%rsp), %r11
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 7c8258e3ad2d..a1a86e782a0e 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -618,9 +618,9 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode)
 1:
 #endif
 	SWAPGS
-	RESTORE_EXTRA_REGS
-	RESTORE_C_REGS
-	REMOVE_PT_GPREGS_FROM_STACK 8
+	POP_EXTRA_REGS
+	POP_C_REGS
+	addq	$8, %rsp	/* skip regs->orig_ax */
 	INTERRUPT_RETURN
 
 
@@ -650,9 +650,9 @@ GLOBAL(restore_regs_and_return_to_kernel)
 	ud2
 1:
 #endif
-	RESTORE_EXTRA_REGS
-	RESTORE_C_REGS
-	REMOVE_PT_GPREGS_FROM_STACK 8
+	POP_EXTRA_REGS
+	POP_C_REGS
+	addq	$8, %rsp	/* skip regs->orig_ax */
 	INTERRUPT_RETURN
 
 ENTRY(native_iret)
-- 
2.14.2