[src/netbsd-8]: src/sys/arch Pull up following revision(s) (requested by maxv...

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

details:   https://anonhg.NetBSD.org/src/rev/44185d47519a
branches:  netbsd-8
changeset: 434517:44185d47519a
user:      snj <snj%NetBSD.org@localhost>
date:      Mon Jan 01 19:09:03 2018 +0000

description:
Pull up following revision(s) (requested by maxv in ticket #477):
        sys/arch/amd64/amd64/machdep.c: revision 1.280
        sys/arch/amd64/include/segments.h: revision 1.34
        sys/arch/i386/i386/machdep.c: revision 1.800
        sys/arch/i386/include/segments.h: revision 1.64 via patch
        sys/arch/x86/x86/vm_machdep.c: revision 1.30
Fix a huge privilege separation vulnerability in Xen-amd64.
On amd64 the kernel runs in ring3, like userland, and therefore SEL_KPL
equals SEL_UPL. While Xen can make a distinction between usermode and
kernelmode in %cs, it can't when it comes to iopl. Since we set SEL_KPL
in iopl, Xen sees SEL_UPL, and allows (unprivileged) userland processes
to read and write to the CPU ports.
It is easy, then, to completely escalate privileges; by reprogramming the
PIC, by reading the ATA disks, by intercepting the keyboard interrupts
(keylogger), etc.
Declare IOPL_KPL, set to 1 on Xen-amd64, which allows the kernel to use
the ports but not userland. I didn't test this change on i386, but it
seems fine enough.

diffstat:

 sys/arch/amd64/amd64/machdep.c    |  6 +++---
 sys/arch/amd64/include/segments.h |  8 +++++++-
 sys/arch/i386/i386/machdep.c      |  6 +++---
 sys/arch/i386/include/segments.h  |  3 ++-
 sys/arch/x86/x86/vm_machdep.c     |  6 +++---
 5 files changed, 18 insertions(+), 11 deletions(-)

diffs (120 lines):

diff -r a2986cc711d6 -r 44185d47519a sys/arch/amd64/amd64/machdep.c
--- a/sys/arch/amd64/amd64/machdep.c    Mon Jan 01 18:58:32 2018 +0000
+++ b/sys/arch/amd64/amd64/machdep.c    Mon Jan 01 19:09:03 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: machdep.c,v 1.255.6.2 2017/11/30 14:03:41 martin Exp $ */
+/*     $NetBSD: machdep.c,v 1.255.6.3 2018/01/01 19:09:03 snj Exp $    */
 
 /*-
  * Copyright (c) 1996, 1997, 1998, 2000, 2006, 2007, 2008, 2011
@@ -111,7 +111,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.255.6.2 2017/11/30 14:03:41 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.255.6.3 2018/01/01 19:09:03 snj Exp $");
 
 /* #define XENDEBUG_LOW  */
 
@@ -473,7 +473,7 @@
        pcb->pcb_fs = 0;
        pcb->pcb_gs = 0;
        pcb->pcb_rsp0 = (uvm_lwp_getuarea(l) + USPACE - 16) & ~0xf;
-       pcb->pcb_iopl = SEL_KPL;
+       pcb->pcb_iopl = IOPL_KPL;
        pcb->pcb_dbregs = NULL;
 
        pmap_kernel()->pm_ldt_sel = GSYSSEL(GLDT_SEL, SEL_KPL);
diff -r a2986cc711d6 -r 44185d47519a sys/arch/amd64/include/segments.h
--- a/sys/arch/amd64/include/segments.h Mon Jan 01 18:58:32 2018 +0000
+++ b/sys/arch/amd64/include/segments.h Mon Jan 01 19:09:03 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: segments.h,v 1.29 2017/02/05 08:58:39 maxv Exp $       */
+/*     $NetBSD: segments.h,v 1.29.6.1 2018/01/01 19:09:03 snj Exp $    */
 
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
@@ -107,6 +107,12 @@
 #define ISLDT(s)       ((s) & SEL_LDT) /* is it local or global */
 #define SEL_LDT                4               /* local descriptor table */
 
+#ifdef XEN
+#define IOPL_KPL       1
+#else
+#define IOPL_KPL       SEL_KPL
+#endif
+
 /* Dynamically allocated TSSs and LDTs start (byte offset) */
 #define SYSSEL_START   (NGDT_MEM << 3)
 #define DYNSEL_START   (SYSSEL_START + (NGDT_SYS << 4))
diff -r a2986cc711d6 -r 44185d47519a sys/arch/i386/i386/machdep.c
--- a/sys/arch/i386/i386/machdep.c      Mon Jan 01 18:58:32 2018 +0000
+++ b/sys/arch/i386/i386/machdep.c      Mon Jan 01 19:09:03 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: machdep.c,v 1.782.6.1 2017/07/05 19:59:29 snj Exp $    */
+/*     $NetBSD: machdep.c,v 1.782.6.2 2018/01/01 19:09:03 snj Exp $    */
 
 /*-
  * Copyright (c) 1996, 1997, 1998, 2000, 2004, 2006, 2008, 2009
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.782.6.1 2017/07/05 19:59:29 snj Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.782.6.2 2018/01/01 19:09:03 snj Exp $");
 
 #include "opt_beep.h"
 #include "opt_compat_ibcs2.h"
@@ -506,7 +506,7 @@
        pmap_kernel()->pm_ldt_sel = GSEL(GLDT_SEL, SEL_KPL);
        pcb->pcb_cr0 = rcr0() & ~CR0_TS;
        pcb->pcb_esp0 = uvm_lwp_getuarea(l) + USPACE - 16;
-       pcb->pcb_iopl = SEL_KPL;
+       pcb->pcb_iopl = IOPL_KPL;
        l->l_md.md_regs = (struct trapframe *)pcb->pcb_esp0 - 1;
        memcpy(&pcb->pcb_fsd, &gdtstore[GUDATA_SEL], sizeof(pcb->pcb_fsd));
        memcpy(&pcb->pcb_gsd, &gdtstore[GUDATA_SEL], sizeof(pcb->pcb_gsd));
diff -r a2986cc711d6 -r 44185d47519a sys/arch/i386/include/segments.h
--- a/sys/arch/i386/include/segments.h  Mon Jan 01 18:58:32 2018 +0000
+++ b/sys/arch/i386/include/segments.h  Mon Jan 01 19:09:03 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: segments.h,v 1.59 2017/02/08 09:39:32 maxv Exp $       */
+/*     $NetBSD: segments.h,v 1.59.6.1 2018/01/01 19:09:04 snj Exp $    */
 
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
@@ -104,6 +104,7 @@
 #endif /* XEN */
 #define ISLDT(s)       ((s) & SEL_LDT) /* is it local or global */
 #define SEL_LDT                4               /* local descriptor table */
+#define IOPL_KPL       SEL_KPL
 #define IDXSEL(s)      (((s) >> 3) & 0x1fff)           /* index of selector */
 #define IDXSELN(s)     (((s) >> 3))                    /* index of selector */
 #define GSEL(s,r)      (((s) << 3) | r)                /* a global selector */
diff -r a2986cc711d6 -r 44185d47519a sys/arch/x86/x86/vm_machdep.c
--- a/sys/arch/x86/x86/vm_machdep.c     Mon Jan 01 18:58:32 2018 +0000
+++ b/sys/arch/x86/x86/vm_machdep.c     Mon Jan 01 19:09:03 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vm_machdep.c,v 1.28 2017/02/23 03:34:22 kamil Exp $    */
+/*     $NetBSD: vm_machdep.c,v 1.28.6.1 2018/01/01 19:09:04 snj Exp $  */
 
 /*-
  * Copyright (c) 1982, 1986 The Regents of the University of California.
@@ -80,7 +80,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.28 2017/02/23 03:34:22 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.28.6.1 2018/01/01 19:09:04 snj Exp $");
 
 #include "opt_mtrr.h"
 
@@ -164,7 +164,7 @@
        pcb2->pcb_dbregs = NULL;
 
 #if defined(XEN)
-       pcb2->pcb_iopl = SEL_KPL;
+       pcb2->pcb_iopl = IOPL_KPL;
 #endif
 
        /*