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

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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>
This commit is contained in:
Ingo Molnar
2006-06-27 02:53:50 -07:00
committed by Linus Torvalds
parent d5fb34261d
commit e6e5494cb2
18 changed files with 235 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
include/asm-i386/elf.h
View File

@@ -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)); \