[src/trunk]: src/sys/arch/x86/x86 Mask mxcsr, otherwise userland could set re...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/22ee1dac94ac
branches:  trunk
changeset: 357217:22ee1dac94ac
user:      maxv <maxv%NetBSD.org@localhost>
date:      Tue Oct 31 18:13:37 2017 +0000

description:
Mask mxcsr, otherwise userland could set reserved bits to 1 and make
xrstor fault.

diffstat:

 sys/arch/x86/x86/fpu.c |  10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diffs (32 lines):

diff -r 2ac54ff1e1a3 -r 22ee1dac94ac sys/arch/x86/x86/fpu.c
--- a/sys/arch/x86/x86/fpu.c    Tue Oct 31 16:10:25 2017 +0000
+++ b/sys/arch/x86/x86/fpu.c    Tue Oct 31 18:13:37 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: fpu.c,v 1.18 2017/10/31 15:16:10 maxv Exp $    */
+/*     $NetBSD: fpu.c,v 1.19 2017/10/31 18:13:37 maxv Exp $    */
 
 /*
  * Copyright (c) 2008 The NetBSD Foundation, Inc.  All
@@ -96,7 +96,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fpu.c,v 1.18 2017/10/31 15:16:10 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fpu.c,v 1.19 2017/10/31 18:13:37 maxv Exp $");
 
 #include "opt_multiprocessor.h"
 
@@ -572,8 +572,12 @@
 
        if (i386_use_fxsave) {
                memcpy(&fpu_save->sv_xmm, fpregs, sizeof(fpu_save->sv_xmm));
-               /* Invalid bits in the mxcsr_mask will cause faults */
+
+               /*
+                * Invalid bits in mxcsr or mxcsr_mask will cause faults.
+                */
                fpu_save->sv_xmm.fx_mxcsr_mask &= __INITIAL_MXCSR_MASK__;
+               fpu_save->sv_xmm.fx_mxcsr &= fpu_save->sv_xmm.fx_mxcsr_mask;
 
                /*
                 * Make sure the x87 and SSE bits are set in xstate_bv.