From 3cdc87ea01fc2d12e6c16d27520d7554cf07dc8e Mon Sep 17 00:00:00 2001
From: emaste <emaste@FreeBSD.org>
Date: Tue, 5 Feb 2019 18:07:45 +0000
Subject: [PATCH] amd64: clear callee-preserved registers on syscall exit

Submitted by:	kib
Approved by:	so
Security:	CVE-2019-5595
Security:	FreeBSD-SA-19:01.syscall
---
 sys/amd64/amd64/exception.S | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/amd64/amd64/exception.S b/sys/amd64/amd64/exception.S
index b7e88e6dc37..c35cea9b849 100644
--- a/sys/amd64/amd64/exception.S
+++ b/sys/amd64/amd64/exception.S
@@ -496,12 +496,14 @@ fast_syscall_common:
 	movq	TF_RFLAGS(%rsp),%r11	/* original %rflags */
 	movq	TF_RIP(%rsp),%rcx	/* original %rip */
 	movq	TF_RSP(%rsp),%rsp	/* user stack pointer */
+	xorl	%r8d,%r8d		/* zero the rest of GPRs */
+	xorl	%r10d,%r10d
 	cmpb	$0,pti
 	je	2f
 	movq	PCPU(UCR3),%r9
 	movq	%r9,%cr3
-	xorl	%r9d,%r9d
-2:	swapgs
+2:	xorl	%r9d,%r9d
+	swapgs
 	sysretq
 
 3:	/* AST scheduled. */
-- 
2.45.0