Module Name:    src
Committed By:   snj
Date:           Mon Feb 19 20:55:45 UTC 2018

Modified Files:
        src/sys/arch/amd64/amd64 [netbsd-6-0]: machdep.c
        src/sys/arch/amd64/include [netbsd-6-0]: segments.h
        src/sys/arch/i386/i386 [netbsd-6-0]: machdep.c
        src/sys/arch/i386/include [netbsd-6-0]: segments.h
        src/sys/arch/x86/x86 [netbsd-6-0]: 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 -r1.175.2.7.2.2 -r1.175.2.7.2.3 \
    src/sys/arch/amd64/amd64/machdep.c
cvs rdiff -u -r1.22 -r1.22.14.1 src/sys/arch/amd64/include/segments.h
cvs rdiff -u -r1.717.2.7.4.1 -r1.717.2.7.4.2 src/sys/arch/i386/i386/machdep.c
cvs rdiff -u -r1.54 -r1.54.16.1 src/sys/arch/i386/include/segments.h
cvs rdiff -u -r1.14 -r1.14.6.1 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:1.175.2.7.2.2 src/sys/arch/amd64/amd64/machdep.c:1.175.2.7.2.3
--- src/sys/arch/amd64/amd64/machdep.c:1.175.2.7.2.2	Tue Aug  8 11:55:20 2017
+++ src/sys/arch/amd64/amd64/machdep.c	Mon Feb 19 20:55:44 2018
@@ -1,4 +1,4 @@
-/*	$NetBSD: machdep.c,v 1.175.2.7.2.2 2017/08/08 11:55:20 martin Exp $	*/
+/*	$NetBSD: machdep.c,v 1.175.2.7.2.3 2018/02/19 20:55:44 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 1.175.2.7.2.2 2017/08/08 11:55:20 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.175.2.7.2.3 2018/02/19 20:55:44 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:1.22.14.1
--- 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 20:55:44 2018
@@ -1,4 +1,4 @@
-/*	$NetBSD: segments.h,v 1.22 2011/02/07 03:54:45 chs Exp $	*/
+/*	$NetBSD: segments.h,v 1.22.14.1 2018/02/19 20:55:44 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:1.717.2.7.4.1 src/sys/arch/i386/i386/machdep.c:1.717.2.7.4.2
--- src/sys/arch/i386/i386/machdep.c:1.717.2.7.4.1	Tue Aug  8 11:55:20 2017
+++ src/sys/arch/i386/i386/machdep.c	Mon Feb 19 20:55:44 2018
@@ -1,4 +1,4 @@
-/*	$NetBSD: machdep.c,v 1.717.2.7.4.1 2017/08/08 11:55:20 martin Exp $	*/
+/*	$NetBSD: machdep.c,v 1.717.2.7.4.2 2018/02/19 20:55:44 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 1.717.2.7.4.1 2017/08/08 11:55:20 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.717.2.7.4.2 2018/02/19 20:55:44 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:1.54.16.1
--- 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 20:55:44 2018
@@ -1,4 +1,4 @@
-/*	$NetBSD: segments.h,v 1.54 2011/04/26 15:51:23 joerg Exp $	*/
+/*	$NetBSD: segments.h,v 1.54.16.1 2018/02/19 20:55:44 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:1.14.6.1
--- 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 20:55:44 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 1.14.6.1 2018/02/19 20:55:44 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 1.14.6.1 2018/02/19 20:55:44 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
 
 	/*

Reply via email to