3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
commit 48be69a026b2c17350a5ef18a1959a919f60be7d upstream.
Move the signal handlers into a VDSO page rather than keeping them in
the vectors page. This allows us to place them randomly within this
page, and also map the page at a random location within userspace
further protecting these code fragments from ROP attacks. The new
VDSO page is also poisoned in the same way as the vector page.
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/include/asm/elf.h | 4 +++
arch/arm/include/asm/mmu.h | 1
arch/arm/kernel/process.c | 40 +++++++++++++++++++++++++++++++++---
arch/arm/kernel/signal.c | 50 +++++++++++++++++++++++++++++++++++++++------
arch/arm/kernel/signal.h | 12 ----------
arch/arm/kernel/traps.c | 9 --------
6 files changed, 86 insertions(+), 30 deletions(-)
--- 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
--- a/arch/arm/include/asm/mmu.h
+++ b/arch/arm/include/asm/mmu.h
@@ -8,6 +8,7 @@ typedef struct {
atomic64_t id;
#endif
unsigned int vmalloc_seq;
+ unsigned long sigpage;
} mm_context_t;
#ifdef CONFIG_CPU_HAS_ASID
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -435,8 +435,8 @@ unsigned long arch_randomize_brk(struct
#ifdef CONFIG_MMU
/*
* 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,
@@ -468,6 +468,40 @@ int in_gate_area_no_mm(unsigned long add
const char *arch_vma_name(struct vm_area_struct *vma)
{
- return (vma == &gate_vma) ? "[vectors]" : NULL;
+ return (vma == &gate_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
--- 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)
{
@@ -397,11 +399,14 @@ setup_return(struct pt_regs *regs, struc
return 1;
if (cpsr & MODE32_BIT) {
+ struct mm_struct *mm = current->mm;
/*
- * 32-bit code can use the new high-page
- * signal return code support.
+ * 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
@@ -603,3 +608,36 @@ do_work_pending(struct pt_regs *regs, un
} 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;
+}
--- 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];
--- 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;
@@ -849,13 +847,6 @@ void __init early_trap_init(void *vector
kuser_init(vectors_base);
- /*
- * 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));
-
flush_icache_range(vectors, vectors + PAGE_SIZE * 2);
modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
}
--
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