Commit e6e5494c authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds

[PATCH] vdso: randomize the i386 vDSO by moving it into a vma

Move the i386 VDSO down into a vma and thus randomize it.

Besides the security implications, this feature also helps debuggers, which
can COW a vma-backed VDSO just like a normal DSO and can thus do
single-stepping and other debugging features.

It's good for hypervisors (Xen, VMWare) too, which typically live in the same
high-mapped address space as the VDSO, hence whenever the VDSO is used, they
get lots of guest pagefaults and have to fix such guest accesses up - which
slows things down instead of speeding things up (the primary purpose of the
VDSO).

There's a new CONFIG_COMPAT_VDSO (default=y) option, which provides support
for older glibcs that still rely on a prelinked high-mapped VDSO.  Newer
distributions (using glibc 2.3.3 or later) can turn this option off.  Turning
it off is also recommended for security reasons: attackers cannot use the
predictable high-mapped VDSO page as syscall trampoline anymore.

There is a new vdso=[0|1] boot option as well, and a runtime
/proc/sys/vm/vdso_enabled sysctl switch, that allows the VDSO to be turned
on/off.

(This version of the VDSO-randomization patch also has working ELF
coredumping, the previous patch crashed in the coredumping code.)

This code is a combined work of the exec-shield VDSO randomization
code and Gerd Hoffmann's hypervisor-centric VDSO patch. Rusty Russell
started this patch and i completed it.

[akpm@osdl.org: cleanups]
[akpm@osdl.org: compile fix]
[akpm@osdl.org: compile fix 2]
[akpm@osdl.org: compile fix 3]
[akpm@osdl.org: revernt MAXMEM change]
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarArjan van de Ven <arjan@infradead.org>
Cc: Gerd Hoffmann <kraxel@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent d5fb3426
......@@ -1669,6 +1669,10 @@ running once the system is up.
usbhid.mousepoll=
[USBHID] The interval which mice are to be polled at.
vdso= [IA-32]
vdso=1: enable VDSO (default)
vdso=0: disable VDSO mapping
video= [FB] Frame buffer configuration
See Documentation/fb/modedb.txt.
......
......@@ -780,6 +780,17 @@ config HOTPLUG_CPU
enable suspend on SMP systems. CPUs can be controlled through
/sys/devices/system/cpu.
config COMPAT_VDSO
bool "Compat VDSO support"
default y
help
Map the VDSO to the predictable old-style address too.
---help---
Say N here if you are running a sufficiently recent glibc
version (2.3.3 or later), to remove the high-mapped
VDSO mapping and to exclusively use the randomized VDSO.
If unsure, say Y.
endmenu
......
......@@ -14,6 +14,7 @@
#include <asm/fixmap.h>
#include <asm/processor.h>
#include <asm/thread_info.h>
#include <asm/elf.h>
#define DEFINE(sym, val) \
asm volatile("\n->" #sym " %0 " #val : : "i" (val))
......@@ -54,6 +55,7 @@ void foo(void)
OFFSET(TI_preempt_count, thread_info, preempt_count);
OFFSET(TI_addr_limit, thread_info, addr_limit);
OFFSET(TI_restart_block, thread_info, restart_block);
OFFSET(TI_sysenter_return, thread_info, sysenter_return);
BLANK();
OFFSET(EXEC_DOMAIN_handler, exec_domain, handler);
......@@ -69,7 +71,7 @@ void foo(void)
sizeof(struct tss_struct));
DEFINE(PAGE_SIZE_asm, PAGE_SIZE);
DEFINE(VSYSCALL_BASE, __fix_to_virt(FIX_VSYSCALL));
DEFINE(VDSO_PRELINK, VDSO_PRELINK);
OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);
}
......@@ -270,7 +270,12 @@ sysenter_past_esp:
pushl $(__USER_CS)
CFI_ADJUST_CFA_OFFSET 4
/*CFI_REL_OFFSET cs, 0*/
pushl $SYSENTER_RETURN
/*
* Push current_thread_info()->sysenter_return to the stack.
* A tiny bit of offset fixup is necessary - 4*4 means the 4 words
* pushed above; +8 corresponds to copy_thread's esp0 setting.
*/
pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)
CFI_ADJUST_CFA_OFFSET 4
CFI_REL_OFFSET eip, 0
......
......@@ -351,7 +351,7 @@ static int setup_frame(int sig, struct k_sigaction *ka,
goto give_sigsegv;
}
restorer = &__kernel_sigreturn;
restorer = (void *)VDSO_SYM(&__kernel_sigreturn);
if (ka->sa.sa_flags & SA_RESTORER)
restorer = ka->sa.sa_restorer;
......@@ -447,7 +447,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
goto give_sigsegv;
/* Set up to return from userspace. */
restorer = &__kernel_rt_sigreturn;
restorer = (void *)VDSO_SYM(&__kernel_rt_sigreturn);
if (ka->sa.sa_flags & SA_RESTORER)
restorer = ka->sa.sa_restorer;
err |= __put_user(restorer, &frame->pretcode);
......
......@@ -2,6 +2,8 @@
* linux/arch/i386/kernel/sysenter.c
*
* (C) Copyright 2002 Linus Torvalds
* Portions based on the vdso-randomization code from exec-shield:
* Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
*
* This file contains the needed initializations to support sysenter.
*/
......@@ -13,12 +15,31 @@
#include <linux/gfp.h>
#include <linux/string.h>
#include <linux/elf.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <asm/cpufeature.h>
#include <asm/msr.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
/*
* Should the kernel map a VDSO page into processes and pass its
* address down to glibc upon exec()?
*/
unsigned int __read_mostly vdso_enabled = 1;
EXPORT_SYMBOL_GPL(vdso_enabled);
static int __init vdso_setup(char *s)
{
vdso_enabled = simple_strtoul(s, NULL, 0);
return 1;
}
__setup("vdso=", vdso_setup);
extern asmlinkage void sysenter_entry(void);
void enable_sep_cpu(void)
......@@ -45,23 +66,122 @@ void enable_sep_cpu(void)
*/
extern const char vsyscall_int80_start, vsyscall_int80_end;
extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
static void *syscall_page;
int __init sysenter_setup(void)
{
void *page = (void *)get_zeroed_page(GFP_ATOMIC);
syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
__set_fixmap(FIX_VSYSCALL, __pa(page), PAGE_READONLY_EXEC);
#ifdef CONFIG_COMPAT_VDSO
__set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY);
printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
#else
/*
* In the non-compat case the ELF coredumping code needs the fixmap:
*/
__set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_KERNEL_RO);
#endif
if (!boot_cpu_has(X86_FEATURE_SEP)) {
memcpy(page,
memcpy(syscall_page,
&vsyscall_int80_start,
&vsyscall_int80_end - &vsyscall_int80_start);
return 0;
}
memcpy(page,
memcpy(syscall_page,
&vsyscall_sysenter_start,
&vsyscall_sysenter_end - &vsyscall_sysenter_start);
return 0;
}
static struct page *syscall_nopage(struct vm_area_struct *vma,
unsigned long adr, int *type)
{
struct page *p = virt_to_page(adr - vma->vm_start + syscall_page);
get_page(p);
return p;
}
/* Prevent VMA merging */
static void syscall_vma_close(struct vm_area_struct *vma)
{
}
static struct vm_operations_struct syscall_vm_ops = {
.close = syscall_vma_close,
.nopage = syscall_nopage,
};
/* Defined in vsyscall-sysenter.S */
extern void SYSENTER_RETURN;
/* Setup a VMA at program startup for the vsyscall page */
int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
{
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long addr;
int ret;
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;
}
vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL);
if (!vma) {
ret = -ENOMEM;
goto up_fail;
}
vma->vm_start = addr;
vma->vm_end = addr + PAGE_SIZE;
/* MAYWRITE to allow gdb to COW and set breakpoints */
vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
vma->vm_flags |= mm->def_flags;
vma->vm_page_prot = protection_map[vma->vm_flags & 7];
vma->vm_ops = &syscall_vm_ops;
vma->vm_mm = mm;
ret = insert_vm_struct(mm, vma);
if (ret)
goto free_vma;
current->mm->context.vdso = (void *)addr;
current_thread_info()->sysenter_return =
(void *)VDSO_SYM(&SYSENTER_RETURN);
mm->total_vm++;
up_fail:
up_write(&mm->mmap_sem);
return ret;
free_vma:
kmem_cache_free(vm_area_cachep, vma);
return ret;
}
const char *arch_vma_name(struct vm_area_struct *vma)
{
if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
return "[vdso]";
return NULL;
}
struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
{
return NULL;
}
int in_gate_area(struct task_struct *task, unsigned long addr)
{
return 0;
}
int in_gate_area_no_task(unsigned long addr)
{
return 0;
}
......@@ -42,10 +42,10 @@ __kernel_vsyscall:
/* 7: align return point with nop's to make disassembly easier */
.space 7,0x90
/* 14: System call restart point is here! (SYSENTER_RETURN - 2) */
/* 14: System call restart point is here! (SYSENTER_RETURN-2) */
jmp .Lenter_kernel
/* 16: System call normal return point is here! */
.globl SYSENTER_RETURN /* Symbol used by entry.S. */
.globl SYSENTER_RETURN /* Symbol used by sysenter.c */
SYSENTER_RETURN:
pop %ebp
.Lpop_ebp:
......
......@@ -7,7 +7,7 @@
SECTIONS
{
. = VSYSCALL_BASE + SIZEOF_HEADERS;
. = VDSO_PRELINK + SIZEOF_HEADERS;
.hash : { *(.hash) } :text
.dynsym : { *(.dynsym) }
......@@ -20,7 +20,7 @@ SECTIONS
For the layouts to match, we need to skip more than enough
space for the dynamic symbol table et al. If this amount
is insufficient, ld -shared will barf. Just increase it here. */
. = VSYSCALL_BASE + 0x400;
. = VDSO_PRELINK + 0x400;
.text : { *(.text) } :text =0x90909090
.note : { *(.note.*) } :text :note
......
......@@ -122,6 +122,11 @@ struct mem_size_stats
unsigned long private_dirty;
};
__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma)
{
return NULL;
}
static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats *mss)
{
struct proc_maps_private *priv = m->private;
......@@ -158,22 +163,23 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats
pad_len_spaces(m, len);
seq_path(m, file->f_vfsmnt, file->f_dentry, "\n");
} else {
if (mm) {
if (vma->vm_start <= mm->start_brk &&
const char *name = arch_vma_name(vma);
if (!name) {
if (mm) {
if (vma->vm_start <= mm->start_brk &&
vma->vm_end >= mm->brk) {
pad_len_spaces(m, len);
seq_puts(m, "[heap]");
} else {
if (vma->vm_start <= mm->start_stack &&
vma->vm_end >= mm->start_stack) {
pad_len_spaces(m, len);
seq_puts(m, "[stack]");
name = "[heap]";
} else if (vma->vm_start <= mm->start_stack &&
vma->vm_end >= mm->start_stack) {
name = "[stack]";
}
} else {
name = "[vdso]";
}
} else {
}
if (name) {
pad_len_spaces(m, len);
seq_puts(m, "[vdso]");
seq_puts(m, name);
}
}
seq_putc(m, '\n');
......
......@@ -10,6 +10,7 @@
#include <asm/processor.h>
#include <asm/system.h> /* for savesegment */
#include <asm/auxvec.h>
#include <asm/desc.h>
#include <linux/utsname.h>
......@@ -129,15 +130,41 @@ extern int dump_task_extended_fpu (struct task_struct *, struct user_fxsr_struct
#define ELF_CORE_COPY_FPREGS(tsk, elf_fpregs) dump_task_fpu(tsk, elf_fpregs)
#define ELF_CORE_COPY_XFPREGS(tsk, elf_xfpregs) dump_task_extended_fpu(tsk, elf_xfpregs)
#define VSYSCALL_BASE (__fix_to_virt(FIX_VSYSCALL))
#define VSYSCALL_EHDR ((const struct elfhdr *) VSYSCALL_BASE)
#define VSYSCALL_ENTRY ((unsigned long) &__kernel_vsyscall)
#define VDSO_HIGH_BASE (__fix_to_virt(FIX_VDSO))
#define VDSO_BASE ((unsigned long)current->mm->context.vdso)
#ifdef CONFIG_COMPAT_VDSO
# define VDSO_COMPAT_BASE VDSO_HIGH_BASE
# define VDSO_PRELINK VDSO_HIGH_BASE
#else
# define VDSO_COMPAT_BASE VDSO_BASE
# define VDSO_PRELINK 0
#endif
#define VDSO_COMPAT_SYM(x) \
(VDSO_COMPAT_BASE + (unsigned long)(x) - VDSO_PRELINK)
#define VDSO_SYM(x) \
(VDSO_BASE + (unsigned long)(x) - VDSO_PRELINK)
#define VDSO_HIGH_EHDR ((const struct elfhdr *) VDSO_HIGH_BASE)
#define VDSO_EHDR ((const struct elfhdr *) VDSO_COMPAT_BASE)
extern void __kernel_vsyscall;
#define VDSO_ENTRY VDSO_SYM(&__kernel_vsyscall)
#define ARCH_HAS_SETUP_ADDITIONAL_PAGES
struct linux_binprm;
extern int arch_setup_additional_pages(struct linux_binprm *bprm,
int executable_stack);
extern unsigned int vdso_enabled;
#define ARCH_DLINFO \
do { \
NEW_AUX_ENT(AT_SYSINFO, VSYSCALL_ENTRY); \
NEW_AUX_ENT(AT_SYSINFO_EHDR, VSYSCALL_BASE); \
do if (vdso_enabled) { \
NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \
NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE); \
} while (0)
/*
......@@ -148,15 +175,15 @@ do { \
* Dumping its extra ELF program headers includes all the other information
* a debugger needs to easily find how the vsyscall DSO was being used.
*/
#define ELF_CORE_EXTRA_PHDRS (VSYSCALL_EHDR->e_phnum)
#define ELF_CORE_EXTRA_PHDRS (VDSO_HIGH_EHDR->e_phnum)
#define ELF_CORE_WRITE_EXTRA_PHDRS \
do { \
const struct elf_phdr *const vsyscall_phdrs = \
(const struct elf_phdr *) (VSYSCALL_BASE \
+ VSYSCALL_EHDR->e_phoff); \
(const struct elf_phdr *) (VDSO_HIGH_BASE \
+ VDSO_HIGH_EHDR->e_phoff); \
int i; \
Elf32_Off ofs = 0; \
for (i = 0; i < VSYSCALL_EHDR->e_phnum; ++i) { \
for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) { \
struct elf_phdr phdr = vsyscall_phdrs[i]; \
if (phdr.p_type == PT_LOAD) { \
BUG_ON(ofs != 0); \
......@@ -174,10 +201,10 @@ do { \
#define ELF_CORE_WRITE_EXTRA_DATA \
do { \
const struct elf_phdr *const vsyscall_phdrs = \
(const struct elf_phdr *) (VSYSCALL_BASE \
+ VSYSCALL_EHDR->e_phoff); \
(const struct elf_phdr *) (VDSO_HIGH_BASE \
+ VDSO_HIGH_EHDR->e_phoff); \
int i; \
for (i = 0; i < VSYSCALL_EHDR->e_phnum; ++i) { \
for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) { \
if (vsyscall_phdrs[i].p_type == PT_LOAD) \
DUMP_WRITE((void *) vsyscall_phdrs[i].p_vaddr, \
PAGE_ALIGN(vsyscall_phdrs[i].p_memsz)); \
......
......@@ -51,7 +51,7 @@
*/
enum fixed_addresses {
FIX_HOLE,
FIX_VSYSCALL,
FIX_VDSO,
#ifdef CONFIG_X86_LOCAL_APIC
FIX_APIC_BASE, /* local (CPU) APIC) -- required for SMP or not */
#endif
......@@ -115,14 +115,6 @@ extern void __set_fixmap (enum fixed_addresses idx,
#define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT))
#define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
/*
* This is the range that is readable by user mode, and things
* acting like user mode such as get_user_pages.
*/
#define FIXADDR_USER_START (__fix_to_virt(FIX_VSYSCALL))
#define FIXADDR_USER_END (FIXADDR_USER_START + PAGE_SIZE)
extern void __this_fixmap_does_not_exist(void);
/*
......
......@@ -12,6 +12,7 @@ typedef struct {
int size;
struct semaphore sem;
void *ldt;
void *vdso;
} mm_context_t;
#endif
......@@ -96,6 +96,8 @@ typedef struct { unsigned long pgprot; } pgprot_t;
#ifndef __ASSEMBLY__
struct vm_area_struct;
/*
* This much address space is reserved for vmalloc() and iomap()
* as well as fixmap mappings.
......@@ -139,6 +141,7 @@ extern int page_is_ram(unsigned long pagenr);
#include <asm-generic/memory_model.h>
#include <asm-generic/page.h>
#define __HAVE_ARCH_GATE_AREA 1
#endif /* __KERNEL__ */
#endif /* _I386_PAGE_H */
......@@ -37,6 +37,7 @@ struct thread_info {
0-0xBFFFFFFF for user-thead
0-0xFFFFFFFF for kernel-thread
*/
void *sysenter_return;
struct restart_block restart_block;
unsigned long previous_esp; /* ESP of the previous stack in case
......
......@@ -78,8 +78,8 @@ static inline int arch_unw_user_mode(const struct unwind_frame_info *info)
return user_mode_vm(&info->regs);
#else
return info->regs.eip < PAGE_OFFSET
|| (info->regs.eip >= __fix_to_virt(FIX_VSYSCALL)
&& info->regs.eip < __fix_to_virt(FIX_VSYSCALL) + PAGE_SIZE)
|| (info->regs.eip >= __fix_to_virt(FIX_VDSO)
&& info->regs.eip < __fix_to_virt(FIX_VDSO) + PAGE_SIZE)
|| info->regs.esp < PAGE_OFFSET;
#endif
}
......
......@@ -1065,5 +1065,7 @@ void drop_slab(void);
extern int randomize_va_space;
#endif
const char *arch_vma_name(struct vm_area_struct *vma);
#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */
......@@ -189,6 +189,7 @@ enum
VM_ZONE_RECLAIM_MODE=31, /* reclaim local zone memory before going off node */
VM_ZONE_RECLAIM_INTERVAL=32, /* time period to wait after reclaim failure */
VM_PANIC_ON_OOM=33, /* panic at out-of-memory */
VM_VDSO_ENABLED=34, /* map VDSO into new processes? */
};
......
......@@ -927,6 +927,18 @@ static ctl_table vm_table[] = {
.proc_handler = &proc_dointvec_jiffies,
.strategy = &sysctl_jiffies,
},
#endif
#ifdef CONFIG_X86_32
{
.ctl_name = VM_VDSO_ENABLED,
.procname = "vdso_enabled",
.data = &vdso_enabled,
.maxlen = sizeof(vdso_enabled),
.mode = 0644,
.proc_handler = &proc_dointvec,
.strategy = &sysctl_intvec,
.extra1 = &zero,
},
#endif
{ .ctl_name = 0 }
};
......
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