Module Name: src
Committed By: snj
Date: Mon Jan 22 19:40:25 UTC 2018
Modified Files:
src/sys/arch/amd64/amd64 [netbsd-7-0]: machdep.c
src/sys/arch/amd64/include [netbsd-7-0]: segments.h
src/sys/arch/i386/i386 [netbsd-7-0]: machdep.c
src/sys/arch/i386/include [netbsd-7-0]: segments.h
src/sys/arch/x86/x86 [netbsd-7-0]: vm_machdep.c
Log Message:
Pull up following revision(s) (requested by maxv in ticket #1550):
sys/arch/amd64/amd64/machdep.c: revision 1.280 via patch
sys/arch/amd64/include/segments.h: revision 1.34 via patch
sys/arch/i386/i386/machdep.c: revision 1.800 via patch
sys/arch/i386/include/segments.h: revision 1.64 via patch
sys/arch/x86/x86/vm_machdep.c: revision 1.30 via patch
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.
To generate a diff of this commit:
cvs rdiff -u -r1.211.6.1 -r1.211.6.2 src/sys/arch/amd64/amd64/machdep.c
cvs rdiff -u -r1.24 -r1.24.16.1 src/sys/arch/amd64/include/segments.h
cvs rdiff -u -r1.752.8.1 -r1.752.8.2 src/sys/arch/i386/i386/machdep.c
cvs rdiff -u -r1.54 -r1.54.34.1 src/sys/arch/i386/include/segments.h
cvs rdiff -u -r1.25.8.1 -r1.25.8.2 src/sys/arch/x86/x86/vm_machdep.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/amd64/amd64/machdep.c
diff -u src/sys/arch/amd64/amd64/machdep.c:1.211.6.1 src/sys/arch/amd64/amd64/machdep.c:1.211.6.2
--- src/sys/arch/amd64/amd64/machdep.c:1.211.6.1 Wed Apr 26 14:50:51 2017
+++ src/sys/arch/amd64/amd64/machdep.c Mon Jan 22 19:40:25 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.211.6.1 2017/04/26 14:50:51 martin Exp $ */
+/* $NetBSD: machdep.c,v 1.211.6.2 2018/01/22 19:40:25 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 1.211.6.1 2017/04/26 14:50:51 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.211.6.2 2018/01/22 19:40:25 snj Exp $");
/* #define XENDEBUG_LOW */
@@ -468,7 +468,7 @@ x86_64_proc0_tss_ldt_init(void)
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;
pmap_kernel()->pm_ldt_sel = GSYSSEL(GLDT_SEL, SEL_KPL);
pcb->pcb_cr0 = rcr0() & ~CR0_TS;
Index: src/sys/arch/amd64/include/segments.h
diff -u src/sys/arch/amd64/include/segments.h:1.24 src/sys/arch/amd64/include/segments.h:1.24.16.1
--- src/sys/arch/amd64/include/segments.h:1.24 Mon Jan 7 17:03:06 2013
+++ src/sys/arch/amd64/include/segments.h Mon Jan 22 19:40:25 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: segments.h,v 1.24 2013/01/07 17:03:06 chs Exp $ */
+/* $NetBSD: segments.h,v 1.24.16.1 2018/01/22 19:40:25 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))
Index: src/sys/arch/i386/i386/machdep.c
diff -u src/sys/arch/i386/i386/machdep.c:1.752.8.1 src/sys/arch/i386/i386/machdep.c:1.752.8.2
--- src/sys/arch/i386/i386/machdep.c:1.752.8.1 Thu Jul 20 01:42:39 2017
+++ src/sys/arch/i386/i386/machdep.c Mon Jan 22 19:40:25 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.752.8.1 2017/07/20 01:42:39 snj Exp $ */
+/* $NetBSD: machdep.c,v 1.752.8.2 2018/01/22 19:40:25 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 1.752.8.1 2017/07/20 01:42:39 snj Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.752.8.2 2018/01/22 19:40:25 snj Exp $");
#include "opt_beep.h"
#include "opt_compat_ibcs2.h"
@@ -502,7 +502,7 @@ i386_proc0_tss_ldt_init(void)
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, &gdt[GUDATA_SEL], sizeof(pcb->pcb_fsd));
memcpy(&pcb->pcb_gsd, &gdt[GUDATA_SEL], sizeof(pcb->pcb_gsd));
Index: src/sys/arch/i386/include/segments.h
diff -u src/sys/arch/i386/include/segments.h:1.54 src/sys/arch/i386/include/segments.h:1.54.34.1
--- src/sys/arch/i386/include/segments.h:1.54 Tue Apr 26 15:51:23 2011
+++ src/sys/arch/i386/include/segments.h Mon Jan 22 19:40:25 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: segments.h,v 1.54 2011/04/26 15:51:23 joerg Exp $ */
+/* $NetBSD: segments.h,v 1.54.34.1 2018/01/22 19:40:25 snj Exp $ */
/*-
* Copyright (c) 1990 The Regents of the University of California.
@@ -104,6 +104,9 @@
#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 */
Index: src/sys/arch/x86/x86/vm_machdep.c
diff -u src/sys/arch/x86/x86/vm_machdep.c:1.25.8.1 src/sys/arch/x86/x86/vm_machdep.c:1.25.8.2
--- src/sys/arch/x86/x86/vm_machdep.c:1.25.8.1 Sun Dec 18 07:02:59 2016
+++ src/sys/arch/x86/x86/vm_machdep.c Mon Jan 22 19:40:25 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: vm_machdep.c,v 1.25.8.1 2016/12/18 07:02:59 snj Exp $ */
+/* $NetBSD: vm_machdep.c,v 1.25.8.2 2018/01/22 19:40:25 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 1.25.8.1 2016/12/18 07:02:59 snj Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.25.8.2 2018/01/22 19:40:25 snj Exp $");
#include "opt_mtrr.h"
@@ -158,7 +158,7 @@ cpu_lwp_fork(struct lwp *l1, struct lwp
fpu_save_area_fork(pcb2, pcb1);
#if defined(XEN)
- pcb2->pcb_iopl = SEL_KPL;
+ pcb2->pcb_iopl = IOPL_KPL;
#endif
/*
