Merge branch 'security-fixes' into fixes

13 files changed, 253 insertions, 99 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 82f069829ac0d7..995b55311c55c3 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -217,7 +217,8 @@ config VECTORS_BASE
 	default DRAM_BASE if REMAP_VECTORS_TO_RAM
 	default 0x00000000
 	help
-	  The base address of exception vectors.
+	  The base address of exception vectors.  This must be two pages
+	  in size.
 
 config ARM_PATCH_PHYS_VIRT
 	bool "Patch physical to virtual translations at runtime" if EMBEDDED
diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
index 38050b1c4800b9..9c9b30717fdaf0 100644
--- a/arch/arm/include/asm/elf.h
+++ b/arch/arm/include/asm/elf.h
@@ -130,4 +130,8 @@ struct mm_struct;
 extern unsigned long arch_randomize_brk(struct mm_struct *mm);
 #define arch_randomize_brk arch_randomize_brk
 
+#define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
+struct linux_binprm;
+int arch_setup_additional_pages(struct linux_binprm *, int);
+
 #endif
diff --git a/arch/arm/include/asm/mmu.h b/arch/arm/include/asm/mmu.h
index d1b4998e4f4398..6f18da09668b5f 100644
--- a/arch/arm/include/asm/mmu.h
+++ b/arch/arm/include/asm/mmu.h
@@ -10,6 +10,7 @@ typedef struct {
 	int		switch_pending;
 #endif
 	unsigned int	vmalloc_seq;
+	unsigned long	sigpage;
 } mm_context_t;
 
 #ifdef CONFIG_CPU_HAS_ASID
diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
index 6363f3d1d50529..4355f0ec44d62e 100644
--- a/arch/arm/include/asm/page.h
+++ b/arch/arm/include/asm/page.h
@@ -142,7 +142,9 @@ extern void __cpu_copy_user_highpage(struct page *to, struct page *from,
 #define clear_page(page)	memset((void *)(page), 0, PAGE_SIZE)
 extern void copy_page(void *to, const void *from);
 
+#ifdef CONFIG_KUSER_HELPERS
 #define __HAVE_ARCH_GATE_AREA 1
+#endif
 
 #ifdef CONFIG_ARM_LPAE
 #include <asm/pgtable-3level-types.h>
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index a39cfc2a1f905f..d40d0ef389db61 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -742,6 +742,18 @@ ENDPROC(__switch_to)
 #endif
 	.endm
 
+	.macro	kuser_pad, sym, size
+	.if	(. - \sym) & 3
+	.rept	4 - (. - \sym) & 3
+	.byte	0
+	.endr
+	.endif
+	.rept	(\size - (. - \sym)) / 4
+	.word	0xe7fddef1
+	.endr
+	.endm
+
+#ifdef CONFIG_KUSER_HELPERS
 	.align	5
 	.globl	__kuser_helper_start
 __kuser_helper_start:
@@ -832,18 +844,13 @@ kuser_cmpxchg64_fixup:
 #error "incoherent kernel configuration"
 #endif
 
-	/* pad to next slot */
-	.rept	(16 - (. - __kuser_cmpxchg64)/4)
-	.word	0
-	.endr
-
-	.align	5
+	kuser_pad __kuser_cmpxchg64, 64
 
 __kuser_memory_barrier:				@ 0xffff0fa0
 	smp_dmb	arm
 	usr_ret	lr
 
-	.align	5
+	kuser_pad __kuser_memory_barrier, 32
 
 __kuser_cmpxchg:				@ 0xffff0fc0
 
@@ -916,13 +923,14 @@ kuser_cmpxchg32_fixup:
 
 #endif
 
-	.align	5
+	kuser_pad __kuser_cmpxchg, 32
 
 __kuser_get_tls:				@ 0xffff0fe0
 	ldr	r0, [pc, #(16 - 8)]	@ read TLS, set in kuser_get_tls_init
 	usr_ret	lr
 	mrc	p15, 0, r0, c13, c0, 3	@ 0xffff0fe8 hardware TLS code
-	.rep	4
+	kuser_pad __kuser_get_tls, 16
+	.rep	3
 	.word	0			@ 0xffff0ff0 software TLS value, then
 	.endr				@ pad up to __kuser_helper_version
 
@@ -932,14 +940,16 @@ __kuser_helper_version:				@ 0xffff0ffc
 	.globl	__kuser_helper_end
 __kuser_helper_end:
 
+#endif
+
  THUMB(	.thumb	)
 
 /*
  * Vector stubs.
  *
- * This code is copied to 0xffff0200 so we can use branches in the
- * vectors, rather than ldr's.  Note that this code must not
- * exceed 0x300 bytes.
+ * This code is copied to 0xffff1000 so we can use branches in the
+ * vectors, rather than ldr's.  Note that this code must not exceed
+ * a page size.
  *
  * Common stub entry macro:
  *   Enter in IRQ mode, spsr = SVC/USR CPSR, lr = SVC/USR PC
@@ -986,8 +996,17 @@ ENDPROC(vector_\name)
 1:
 	.endm
 
-	.globl	__stubs_start
+	.section .stubs, "ax", %progbits
 __stubs_start:
+	@ This must be the first word
+	.word	vector_swi
+
+vector_rst:
+ ARM(	swi	SYS_ERROR0	)
+ THUMB(	svc	#0		)
+ THUMB(	nop			)
+	b	vector_und
+
 /*
  * Interrupt dispatcher
  */
@@ -1082,6 +1101,16 @@ __stubs_start:
 	.align	5
 
 /*=============================================================================
+ * Address exception handler
+ *-----------------------------------------------------------------------------
+ * These aren't too critical.
+ * (they're not supposed to happen, and won't happen in 32-bit data mode).
+ */
+
+vector_addrexcptn:
+	b	vector_addrexcptn
+
+/*=============================================================================
  * Undefined FIQs
  *-----------------------------------------------------------------------------
  * Enter in FIQ mode, spsr = ANY CPSR, lr = ANY PC
@@ -1094,45 +1123,19 @@ __stubs_start:
 vector_fiq:
 	subs	pc, lr, #4
 
-/*=============================================================================
- * Address exception handler
- *-----------------------------------------------------------------------------
- * These aren't too critical.
- * (they're not supposed to happen, and won't happen in 32-bit data mode).
- */
-
-vector_addrexcptn:
-	b	vector_addrexcptn
-
-/*
- * We group all the following data together to optimise
- * for CPUs with separate I & D caches.
- */
-	.align	5
-
-.LCvswi:
-	.word	vector_swi
-
-	.globl	__stubs_end
-__stubs_end:
-
-	.equ	stubs_offset, __vectors_start + 0x200 - __stubs_start
+	.globl	vector_fiq_offset
+	.equ	vector_fiq_offset, vector_fiq
 
-	.globl	__vectors_start
+	.section .vectors, "ax", %progbits
 __vectors_start:
- ARM(	swi	SYS_ERROR0	)
- THUMB(	svc	#0		)
- THUMB(	nop			)
-	W(b)	vector_und + stubs_offset
-	W(ldr)	pc, .LCvswi + stubs_offset
-	W(b)	vector_pabt + stubs_offset
-	W(b)	vector_dabt + stubs_offset
-	W(b)	vector_addrexcptn + stubs_offset
-	W(b)	vector_irq + stubs_offset
-	W(b)	vector_fiq + stubs_offset
-
-	.globl	__vectors_end
-__vectors_end:
+	W(b)	vector_rst
+	W(b)	vector_und
+	W(ldr)	pc, __vectors_start + 0x1000
+	W(b)	vector_pabt
+	W(b)	vector_dabt
+	W(b)	vector_addrexcptn
+	W(b)	vector_irq
+	W(b)	vector_fiq
 
 	.data
 
diff --git a/arch/arm/kernel/fiq.c b/arch/arm/kernel/fiq.c
index 2adda11f712fe0..25442f451148ee 100644
--- a/arch/arm/kernel/fiq.c
+++ b/arch/arm/kernel/fiq.c
@@ -47,6 +47,11 @@
 #include <asm/irq.h>
 #include <asm/traps.h>
 
+#define FIQ_OFFSET ({					\
+		extern void *vector_fiq_offset;		\
+		(unsigned)&vector_fiq_offset;		\
+	})
+
 static unsigned long no_fiq_insn;
 
 /* Default reacquire function
@@ -80,13 +85,16 @@ int show_fiq_list(struct seq_file *p, int prec)
 void set_fiq_handler(void *start, unsigned int length)
 {
 #if defined(CONFIG_CPU_USE_DOMAINS)
-	memcpy((void *)0xffff001c, start, length);
+	void *base = (void *)0xffff0000;
 #else
-	memcpy(vectors_page + 0x1c, start, length);
+	void *base = vectors_page;
 #endif
-	flush_icache_range(0xffff001c, 0xffff001c + length);
+	unsigned offset = FIQ_OFFSET;
+
+	memcpy(base + offset, start, length);
+	flush_icache_range(0xffff0000 + offset, 0xffff0000 + offset + length);
 	if (!vectors_high())
-		flush_icache_range(0x1c, 0x1c + length);
+		flush_icache_range(offset, offset + length);
 }
 
 int claim_fiq(struct fiq_handler *f)
@@ -144,6 +152,7 @@ EXPORT_SYMBOL(disable_fiq);
 
 void __init init_FIQ(int start)
 {
-	no_fiq_insn = *(unsigned long *)0xffff001c;
+	unsigned offset = FIQ_OFFSET;
+	no_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
 	fiq_start = start;
 }
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 08b47ebd31440f..16ed3f7c4980a8 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -429,10 +429,11 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
 }
 
 #ifdef CONFIG_MMU
+#ifdef CONFIG_KUSER_HELPERS
 /*
  * The vectors page is always readable from user space for the
- * atomic helpers and the signal restart code. Insert it into the
- * gate_vma so that it is visible through ptrace and /proc/<pid>/mem.
+ * atomic helpers. Insert it into the gate_vma so that it is visible
+ * through ptrace and /proc/<pid>/mem.
  */
 static struct vm_area_struct gate_vma = {
 	.vm_start	= 0xffff0000,
@@ -461,9 +462,47 @@ int in_gate_area_no_mm(unsigned long addr)
 {
 	return in_gate_area(NULL, addr);
 }
+#define is_gate_vma(vma)	((vma) = &gate_vma)
+#else
+#define is_gate_vma(vma)	0
+#endif
 
 const char *arch_vma_name(struct vm_area_struct *vma)
 {
-	return (vma == &gate_vma) ? "[vectors]" : NULL;
+	return is_gate_vma(vma) ? "[vectors]" :
+		(vma->vm_mm && vma->vm_start == vma->vm_mm->context.sigpage) ?
+		 "[sigpage]" : NULL;
+}
+
+extern struct page *get_signal_page(void);
+
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+	struct mm_struct *mm = current->mm;
+	struct page *page;
+	unsigned long addr;
+	int ret;
+
+	page = get_signal_page();
+	if (!page)
+		return -ENOMEM;
+
+	down_write(&mm->mmap_sem);
+	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
+	if (IS_ERR_VALUE(addr)) {
+		ret = addr;
+		goto up_fail;
+	}
+
+	ret = install_special_mapping(mm, addr, PAGE_SIZE,
+		VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
+		&page);
+
+	if (ret == 0)
+		mm->context.sigpage = addr;
+
+ up_fail:
+	up_write(&mm->mmap_sem);
+	return ret;
 }
 #endif
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 1c16c35c271af5..0f17e06d51e60e 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -8,6 +8,7 @@
  * published by the Free Software Foundation.
  */
 #include <linux/errno.h>
+#include <linux/random.h>
 #include <linux/signal.h>
 #include <linux/personality.h>
 #include <linux/uaccess.h>
@@ -15,12 +16,11 @@
 
 #include <asm/elf.h>
 #include <asm/cacheflush.h>
+#include <asm/traps.h>
 #include <asm/ucontext.h>
 #include <asm/unistd.h>
 #include <asm/vfp.h>
 
-#include "signal.h"
-
 /*
  * For ARM syscalls, we encode the syscall number into the instruction.
  */
@@ -40,11 +40,13 @@
 #define SWI_THUMB_SIGRETURN	(0xdf00 << 16 | 0x2700 | (__NR_sigreturn - __NR_SYSCALL_BASE))
 #define SWI_THUMB_RT_SIGRETURN	(0xdf00 << 16 | 0x2700 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))
 
-const unsigned long sigreturn_codes[7] = {
+static const unsigned long sigreturn_codes[7] = {
 	MOV_R7_NR_SIGRETURN,    SWI_SYS_SIGRETURN,    SWI_THUMB_SIGRETURN,
 	MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
 };
 
+static unsigned long signal_return_offset;
+
 #ifdef CONFIG_CRUNCH
 static int preserve_crunch_context(struct crunch_sigframe __user *frame)
 {
@@ -401,12 +403,15 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
 			return 1;
 
 		if ((cpsr & MODE32_BIT) && !IS_ENABLED(CONFIG_ARM_MPU)) {
+			struct mm_struct *mm = current->mm;
+
 			/*
-			 * 32-bit code can use the new high-page
-			 * signal return code support except when the MPU has
-			 * protected the vectors page from PL0
+			 * 32-bit code can use the signal return page
+			 * except when the MPU has protected the vectors
+			 * page from PL0
 			 */
-			retcode = KERN_SIGRETURN_CODE + (idx << 2) + thumb;
+			retcode = mm->context.sigpage + signal_return_offset +
+				  (idx << 2) + thumb;
 		} else {
 			/*
 			 * Ensure that the instruction cache sees
@@ -608,3 +613,36 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 	} while (thread_flags & _TIF_WORK_MASK);
 	return 0;
 }
+
+static struct page *signal_page;
+
+struct page *get_signal_page(void)
+{
+	if (!signal_page) {
+		unsigned long ptr;
+		unsigned offset;
+		void *addr;
+
+		signal_page = alloc_pages(GFP_KERNEL, 0);
+
+		if (!signal_page)
+			return NULL;
+
+		addr = page_address(signal_page);
+
+		/* Give the signal return code some randomness */
+		offset = 0x200 + (get_random_int() & 0x7fc);
+		signal_return_offset = offset;
+
+		/*
+		 * Copy signal return handlers into the vector page, and
+		 * set sigreturn to be a pointer to these.
+		 */
+		memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
+
+		ptr = (unsigned long)addr + offset;
+		flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
+	}
+
+	return signal_page;
+}
diff --git a/arch/arm/kernel/signal.h b/arch/arm/kernel/signal.h
deleted file mode 100644
index 5ff067b7c7522f..00000000000000
--- a/arch/arm/kernel/signal.h
+++ /dev/null
@@ -1,12 +0,0 @@
-/*
- *  linux/arch/arm/kernel/signal.h
- *
- *  Copyright (C) 2005-2009 Russell King.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-#define KERN_SIGRETURN_CODE	(CONFIG_VECTORS_BASE + 0x00000500)
-
-extern const unsigned long sigreturn_codes[7];
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index cab094c234ee85..ab517fcce21b83 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -35,8 +35,6 @@
 #include <asm/tls.h>
 #include <asm/system_misc.h>
 
-#include "signal.h"
-
 static const char *handler[]= { "prefetch abort", "data abort", "address exception", "interrupt" };
 
 void *vectors_page;
@@ -800,15 +798,26 @@ void __init trap_init(void)
 	return;
 }
 
-static void __init kuser_get_tls_init(unsigned long vectors)
+#ifdef CONFIG_KUSER_HELPERS
+static void __init kuser_init(void *vectors)
 {
+	extern char __kuser_helper_start[], __kuser_helper_end[];
+	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
+
+	memcpy(vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
+
 	/*
 	 * vectors + 0xfe0 = __kuser_get_tls
 	 * vectors + 0xfe8 = hardware TLS instruction at 0xffff0fe8
 	 */
 	if (tls_emu || has_tls_reg)
-		memcpy((void *)vectors + 0xfe0, (void *)vectors + 0xfe8, 4);
+		memcpy(vectors + 0xfe0, vectors + 0xfe8, 4);
 }
+#else
+static void __init kuser_init(void *vectors)
+{
+}
+#endif
 
 void __init early_trap_init(void *vectors_base)
 {
@@ -816,33 +825,30 @@ void __init early_trap_init(void *vectors_base)
 	unsigned long vectors = (unsigned long)vectors_base;
 	extern char __stubs_start[], __stubs_end[];
 	extern char __vectors_start[], __vectors_end[];
-	extern char __kuser_helper_start[], __kuser_helper_end[];
-	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
+	unsigned i;
 
 	vectors_page = vectors_base;
 
 	/*
+	 * Poison the vectors page with an undefined instruction.  This
+	 * instruction is chosen to be undefined for both ARM and Thumb
+	 * ISAs.  The Thumb version is an undefined instruction with a
+	 * branch back to the undefined instruction.
+	 */
+	for (i = 0; i < PAGE_SIZE / sizeof(u32); i++)
+		((u32 *)vectors_base)[i] = 0xe7fddef1;
+
+	/*
 	 * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
 	 * into the vector page, mapped at 0xffff0000, and ensure these
 	 * are visible to the instruction stream.
 	 */
 	memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
-	memcpy((void *)vectors + 0x200, __stubs_start, __stubs_end - __stubs_start);
-	memcpy((void *)vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
+	memcpy((void *)vectors + 0x1000, __stubs_start, __stubs_end - __stubs_start);
 
-	/*
-	 * Do processor specific fixups for the kuser helpers
-	 */
-	kuser_get_tls_init(vectors);
-
-	/*
-	 * Copy signal return handlers into the vector page, and
-	 * set sigreturn to be a pointer to these.
-	 */
-	memcpy((void *)(vectors + KERN_SIGRETURN_CODE - CONFIG_VECTORS_BASE),
-	       sigreturn_codes, sizeof(sigreturn_codes));
+	kuser_init(vectors_base);
 
-	flush_icache_range(vectors, vectors + PAGE_SIZE);
+	flush_icache_range(vectors, vectors + PAGE_SIZE * 2);
 	modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
 #else /* ifndef CONFIG_CPU_V7M */
 	/*
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index fa25e4e425f607..7bcee5c9b6049c 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -148,6 +148,23 @@ SECTIONS
 	. = ALIGN(PAGE_SIZE);
 	__init_begin = .;
 #endif
+	/*
+	 * The vectors and stubs are relocatable code, and the
+	 * only thing that matters is their relative offsets
+	 */
+	__vectors_start = .;
+	.vectors 0 : AT(__vectors_start) {
+		*(.vectors)
+	}
+	. = __vectors_start + SIZEOF(.vectors);
+	__vectors_end = .;
+
+	__stubs_start = .;
+	.stubs 0x1000 : AT(__stubs_start) {
+		*(.stubs)
+	}
+	. = __stubs_start + SIZEOF(.stubs);
+	__stubs_end = .;
 
 	INIT_TEXT_SECTION(8)
 	.exit.text : {
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 6cacdc8dd654dd..db5c2cab8fda42 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -421,24 +421,28 @@ config CPU_32v3
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v4
 	bool
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v4T
 	bool
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v5
 	bool
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v6
 	bool
@@ -776,6 +780,7 @@ config CPU_BPREDICT_DISABLE
 
 config TLS_REG_EMUL
 	bool
+	select NEED_KUSER_HELPERS
 	help
 	  An SMP system using a pre-ARMv6 processor (there are apparently
 	  a few prototypes like that in existence) and therefore access to
@@ -783,11 +788,40 @@ config TLS_REG_EMUL
 
 config NEEDS_SYSCALL_FOR_CMPXCHG
 	bool
+	select NEED_KUSER_HELPERS
 	help
 	  SMP on a pre-ARMv6 processor?  Well OK then.
 	  Forget about fast user space cmpxchg support.
 	  It is just not possible.
 
+config NEED_KUSER_HELPERS
+	bool
+
+config KUSER_HELPERS
+	bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
+	default y
+	help
+	  Warning: disabling this option may break user programs.
+
+	  Provide kuser helpers in the vector page.  The kernel provides
+	  helper code to userspace in read only form at a fixed location
+	  in the high vector page to allow userspace to be independent of
+	  the CPU type fitted to the system.  This permits binaries to be
+	  run on ARMv4 through to ARMv7 without modification.
+
+	  However, the fixed address nature of these helpers can be used
+	  by ROP (return orientated programming) authors when creating
+	  exploits.
+
+	  If all of the binaries and libraries which run on your platform
+	  are built specifically for your platform, and make no use of
+	  these helpers, then you can turn this option off.  However,
+	  when such an binary or library is run, it will receive a SIGILL
+	  signal, which will terminate the program.
+
+	  Say N here only if you are absolutely certain that you do not
+	  need these helpers; otherwise, the safe option is to say Y.
+
 config DMA_CACHE_RWFO
 	bool "Enable read/write for ownership DMA cache maintenance"
 	depends on CPU_V6K && SMP
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index b3fdb63783e373..53cdbd39ec8e23 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1195,7 +1195,7 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 	/*
 	 * Allocate the vector page early.
 	 */
-	vectors = early_alloc(PAGE_SIZE);
+	vectors = early_alloc(PAGE_SIZE * 2);
 
 	early_trap_init(vectors);
 
@@ -1240,15 +1240,27 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 	map.pfn = __phys_to_pfn(virt_to_phys(vectors));
 	map.virtual = 0xffff0000;
 	map.length = PAGE_SIZE;
+#ifdef CONFIG_KUSER_HELPERS
 	map.type = MT_HIGH_VECTORS;
+#else
+	map.type = MT_LOW_VECTORS;
+#endif
 	create_mapping(&map);
 
 	if (!vectors_high()) {
 		map.virtual = 0;
+		map.length = PAGE_SIZE * 2;
 		map.type = MT_LOW_VECTORS;
 		create_mapping(&map);
 	}
 
+	/* Now create a kernel read-only mapping */
+	map.pfn += 1;
+	map.virtual = 0xffff0000 + PAGE_SIZE;
+	map.length = PAGE_SIZE;
+	map.type = MT_LOW_VECTORS;
+	create_mapping(&map);
+
 	/*
 	 * Ask the machine support to map in the statically mapped devices.
 	 */