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: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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.
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
#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))
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);
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);
}
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
goto give_sigsegv;
}
- restorer = &__kernel_sigreturn;
+ restorer = (void *)VDSO_SYM(&__kernel_sigreturn);
if (ka->sa.sa_flags & SA_RESTORER)
restorer = ka->sa.sa_restorer;
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);
* 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.
*/
#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)
*/
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;
+}
/* 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:
SECTIONS
{
- . = VSYSCALL_BASE + SIZEOF_HEADERS;
+ . = VDSO_PRELINK + SIZEOF_HEADERS;
.hash : { *(.hash) } :text
.dynsym : { *(.dynsym) }
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
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;
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');
#include <asm/processor.h>
#include <asm/system.h> /* for savesegment */
#include <asm/auxvec.h>
+#include <asm/desc.h>
#include <linux/utsname.h>
#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)
/*
* 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); \
#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)); \
*/
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
#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);
/*
int size;
struct semaphore sem;
void *ldt;
+ void *vdso;
} mm_context_t;
#endif
#ifndef __ASSEMBLY__
+struct vm_area_struct;
+
/*
* This much address space is reserved for vmalloc() and iomap()
* as well as fixmap mappings.
#include <asm-generic/memory_model.h>
#include <asm-generic/page.h>
+#define __HAVE_ARCH_GATE_AREA 1
#endif /* __KERNEL__ */
#endif /* _I386_PAGE_H */
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
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
}
extern int randomize_va_space;
#endif
+const char *arch_vma_name(struct vm_area_struct *vma);
+
#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */
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? */
};
.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 }
};
projects / linux-2.6 / commitdiff