[src/netbsd-8]: src/sys/compat/linux32/arch/amd64 Pull up following revision(...

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

details:   https://anonhg.NetBSD.org/src/rev/32cdfd68781f
branches:  netbsd-8
changeset: 851011:32cdfd68781f
user:      snj <snj%NetBSD.org@localhost>
date:      Sat Sep 09 17:01:23 2017 +0000

description:
Pull up following revision(s) (requested by maxv in ticket #270):
        sys/compat/linux32/arch/amd64/linux32_machdep.c: revision 1.39
Fix a ring0 escalation vulnerability in compat_linux32 where the
index of %cs is controlled by userland, making it easy to trigger
the page fault and get kernel privileges.

diffstat:

 sys/compat/linux32/arch/amd64/linux32_machdep.c |  9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diffs (30 lines):

diff -r 72b2c68e570e -r 32cdfd68781f sys/compat/linux32/arch/amd64/linux32_machdep.c
--- a/sys/compat/linux32/arch/amd64/linux32_machdep.c   Mon Sep 04 20:47:59 2017 +0000
+++ b/sys/compat/linux32/arch/amd64/linux32_machdep.c   Sat Sep 09 17:01:23 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux32_machdep.c,v 1.38 2017/02/05 08:52:11 maxv Exp $ */
+/*     $NetBSD: linux32_machdep.c,v 1.38.6.1 2017/09/09 17:01:23 snj Exp $ */
 
 /*-
  * Copyright (c) 2006 Emmanuel Dreyfus, all rights reserved.
@@ -31,7 +31,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux32_machdep.c,v 1.38 2017/02/05 08:52:11 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux32_machdep.c,v 1.38.6.1 2017/09/09 17:01:23 snj Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -417,8 +417,9 @@
        /*
         * Check for security violations.
         */
-       if (((scp->sc_eflags ^ tf->tf_rflags) & PSL_USERSTATIC) != 0 ||
-           !USERMODE(scp->sc_cs, scp->sc_eflags))
+       if (((scp->sc_eflags ^ tf->tf_rflags) & PSL_USERSTATIC) != 0)
+               return EINVAL;
+       if (!VALID_USER_CSEL32(scp->sc_cs))
                return EINVAL;
 
        if (scp->sc_fs != 0 && !VALID_USER_DSEL32(scp->sc_fs) &&