Module Name: src
Committed By: snj
Date: Mon Feb 19 20:54:38 UTC 2018
Modified Files:
src/sys/arch/amd64/amd64 [netbsd-6]: machdep.c
src/sys/arch/amd64/include [netbsd-6]: segments.h
src/sys/arch/i386/i386 [netbsd-6]: machdep.c
src/sys/arch/i386/include [netbsd-6]: segments.h
src/sys/arch/x86/x86 [netbsd-6]: vm_machdep.c
Log Message:
Pull up following revision(s) (requested by maxv in ticket #1517):
sys/arch/amd64/amd64/machdep.c: 1.280 via patch
sys/arch/amd64/include/segments.h: 1.34 via patch
sys/arch/i386/i386/machdep.c: 1.800
sys/arch/i386/include/segments.h: 1.64
sys/arch/x86/x86/vm_machdep.c: 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.
To generate a diff of this commit:
cvs rdiff -u -r1.175.2.9 -r1.175.2.10 src/sys/arch/amd64/amd64/machdep.c
cvs rdiff -u -r1.22 -r1.22.10.1 src/sys/arch/amd64/include/segments.h
cvs rdiff -u -r1.717.2.8 -r1.717.2.9 src/sys/arch/i386/i386/machdep.c
cvs rdiff -u -r1.54 -r1.54.10.1 src/sys/arch/i386/include/segments.h
cvs rdiff -u -r1.14 -r1.14.2.1 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:1.175.2.9 src/sys/arch/amd64/amd64/machdep.c:1.175.2.10
--- src/sys/arch/amd64/amd64/machdep.c:1.175.2.9 Tue Aug 8 12:00:35 2017
+++ src/sys/arch/amd64/amd64/machdep.c Mon Feb 19 20:54:37 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.175.2.9 2017/08/08 12:00:35 martin Exp $ */
+/* $NetBSD: machdep.c,v 1.175.2.10 2018/02/19 20:54:37 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 1.175.2.9 2017/08/08 12:00:35 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.175.2.10 2018/02/19 20:54:37 snj Exp $");
/* #define XENDEBUG_LOW */
@@ -477,7 +477,7 @@ x86_64_proc0_tss_ldt_init(void)
pcb->pcb_fs = 0;
pcb->pcb_gs = 0;
pcb->pcb_rsp0 = (uvm_lwp_getuarea(l) + KSTACK_SIZE - 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:1.22 src/sys/arch/amd64/include/segments.h:1.22.10.1
--- src/sys/arch/amd64/include/segments.h:1.22 Mon Feb 7 03:54:45 2011
+++ src/sys/arch/amd64/include/segments.h Mon Feb 19 20:54:37 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: segments.h,v 1.22 2011/02/07 03:54:45 chs Exp $ */
+/* $NetBSD: segments.h,v 1.22.10.1 2018/02/19 20:54:37 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:1.717.2.8 src/sys/arch/i386/i386/machdep.c:1.717.2.9
--- src/sys/arch/i386/i386/machdep.c:1.717.2.8 Tue Aug 8 12:00:35 2017
+++ src/sys/arch/i386/i386/machdep.c Mon Feb 19 20:54:38 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.717.2.8 2017/08/08 12:00:35 martin Exp $ */
+/* $NetBSD: machdep.c,v 1.717.2.9 2018/02/19 20:54:38 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 1.717.2.8 2017/08/08 12:00:35 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.717.2.9 2018/02/19 20:54:38 snj Exp $");
#include "opt_beep.h"
#include "opt_compat_ibcs2.h"
@@ -509,7 +509,7 @@ 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) + KSTACK_SIZE - 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:1.54.10.1
--- src/sys/arch/i386/include/segments.h:1.54 Tue Apr 26 15:51:23 2011
+++ src/sys/arch/i386/include/segments.h Mon Feb 19 20:54:38 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: segments.h,v 1.54 2011/04/26 15:51:23 joerg Exp $ */
+/* $NetBSD: segments.h,v 1.54.10.1 2018/02/19 20:54:38 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:1.14 src/sys/arch/x86/x86/vm_machdep.c:1.14.2.1
--- src/sys/arch/x86/x86/vm_machdep.c:1.14 Sat Jan 21 16:48:57 2012
+++ src/sys/arch/x86/x86/vm_machdep.c Mon Feb 19 20:54:38 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: vm_machdep.c,v 1.14 2012/01/21 16:48:57 chs Exp $ */
+/* $NetBSD: vm_machdep.c,v 1.14.2.1 2018/02/19 20:54:38 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 1.14 2012/01/21 16:48:57 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vm_machdep.c,v 1.14.2.1 2018/02/19 20:54:38 snj Exp $");
#include "opt_mtrr.h"
@@ -165,7 +165,7 @@ cpu_lwp_fork(struct lwp *l1, struct lwp
memcpy(pcb2, pcb1, sizeof(struct pcb));
#if defined(XEN)
- pcb2->pcb_iopl = SEL_KPL;
+ pcb2->pcb_iopl = IOPL_KPL;
#endif
/*
