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mm: split ET_DYN ASLR from mmap ASLR

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This fixes the "offset2lib" weakness in ASLR for arm, arm64, mips,
powerpc, and x86.  The problem is that if there is a leak of ASLR from
the executable (ET_DYN), it means a leak of shared library offset as
well (mmap), and vice versa.  Further details and a PoC of this attack
is available here:

  http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html

With this patch, a PIE linked executable (ET_DYN) has its own ASLR
region:

  $ ./show_mmaps_pie
  54859ccd6000-54859ccd7000 r-xp  ...  /tmp/show_mmaps_pie
  54859ced6000-54859ced7000 r--p  ...  /tmp/show_mmaps_pie
  54859ced7000-54859ced8000 rw-p  ...  /tmp/show_mmaps_pie
  7f75be764000-7f75be91f000 r-xp  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75be91f000-7f75beb1f000 ---p  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75beb1f000-7f75beb23000 r--p  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75beb23000-7f75beb25000 rw-p  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75beb25000-7f75beb2a000 rw-p  ...
  7f75beb2a000-7f75beb4d000 r-xp  ...  /lib64/ld-linux-x86-64.so.2
  7f75bed45000-7f75bed46000 rw-p  ...
  7f75bed46000-7f75bed47000 r-xp  ...
  7f75bed47000-7f75bed4c000 rw-p  ...
  7f75bed4c000-7f75bed4d000 r--p  ...  /lib64/ld-linux-x86-64.so.2
  7f75bed4d000-7f75bed4e000 rw-p  ...  /lib64/ld-linux-x86-64.so.2
  7f75bed4e000-7f75bed4f000 rw-p  ...
  7fffb3741000-7fffb3762000 rw-p  ...  [stack]
  7fffb377b000-7fffb377d000 r--p  ...  [vvar]
  7fffb377d000-7fffb377f000 r-xp  ...  [vdso]

The change is to add a call the newly created arch_mmap_rnd() into the
ELF loader for handling ET_DYN ASLR in a separate region from mmap ASLR,
as was already done on s390.  Removes CONFIG_BINFMT_ELF_RANDOMIZE_PIE,
which is no longer needed.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Hector Marco-Gisbert <hecmargi@upv.es>
Cc: Russell King <linux@arm.linux.org.uk>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: "David A. Long" <dave.long@linaro.org>
Cc: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Arun Chandran <achandran@mvista.com>
Cc: Yann Droneaud <ydroneaud@opteya.com>
Cc: Min-Hua Chen <orca.chen@gmail.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Alex Smith <alex@alex-smith.me.uk>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Vineeth Vijayan <vvijayan@mvista.com>
Cc: Jeff Bailey <jeffbailey@google.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Behan Webster <behanw@converseincode.com>
Cc: Ismael Ripoll <iripoll@upv.es>
Cc: Jan-Simon Mller <dl9pf@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kees Cook 2015-04-14 15:48:07 -07:00 committed by Linus Torvalds
parent c6f5b001e6
commit d1fd836dcf
9 changed files with 6 additions and 33 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
arch/arm/Kconfig
View file

@ -1,7 +1,6 @@
config ARM
bool
default y
select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST

1
arch/arm64/Kconfig
View file

@ -1,6 +1,5 @@
config ARM64
def_bool y
select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_GCOV_PROFILE_ALL

1
arch/mips/Kconfig
View file

@ -23,7 +23,6 @@ config MIPS
select HAVE_KRETPROBES
select HAVE_DEBUG_KMEMLEAK
select HAVE_SYSCALL_TRACEPOINTS
select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select ARCH_HAS_ELF_RANDOMIZE
select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES && 64BIT
select RTC_LIB if !MACH_LOONGSON

1
arch/powerpc/Kconfig
View file

@ -88,7 +88,6 @@ config PPC
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_MIGHT_HAVE_PC_SERIO
select BINFMT_ELF
select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select ARCH_HAS_ELF_RANDOMIZE
select OF
select OF_EARLY_FLATTREE

5
arch/s390/include/asm/elf.h
View file

@ -163,10 +163,9 @@ extern unsigned int vdso_enabled;
the loader. We need to make sure that it is out of the way of the program
that it will "exec", and that there is sufficient room for the brk. 64-bit
tasks are aligned to 4GB. */
extern unsigned long randomize_et_dyn(void);
#define ELF_ET_DYN_BASE (randomize_et_dyn() + (is_32bit_task() ? \
#define ELF_ET_DYN_BASE (is_32bit_task() ? \
(STACK_TOP / 3 * 2) : \
(STACK_TOP / 3 * 2) & ~((1UL << 32) - 1)))
(STACK_TOP / 3 * 2) & ~((1UL << 32) - 1))
/* This yields a mask that user programs can use to figure out what
instruction set this CPU supports. */

8
arch/s390/mm/mmap.c
View file

@ -177,14 +177,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
return addr;
}
unsigned long randomize_et_dyn(void)
{
if (current->flags & PF_RANDOMIZE)
return arch_mmap_rnd();
return 0UL;
}
#ifndef CONFIG_64BIT
/*

1
arch/x86/Kconfig
View file

@ -87,7 +87,6 @@ config X86
select HAVE_ARCH_KMEMCHECK
select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP
select HAVE_USER_RETURN_NOTIFIER
select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select ARCH_HAS_ELF_RANDOMIZE
select HAVE_ARCH_JUMP_LABEL
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE

3
fs/Kconfig.binfmt
View file

@ -27,9 +27,6 @@ config COMPAT_BINFMT_ELF
bool
depends on COMPAT && BINFMT_ELF
config ARCH_BINFMT_ELF_RANDOMIZE_PIE
bool
config ARCH_BINFMT_ELF_STATE
bool

18
fs/binfmt_elf.c
View file

@ -31,6 +31,7 @@
#include <linux/security.h>
#include <linux/random.h>
#include <linux/elf.h>
#include <linux/elf-randomize.h>
#include <linux/utsname.h>
#include <linux/coredump.h>
#include <linux/sched.h>
@ -910,21 +911,10 @@ static int load_elf_binary(struct linux_binprm *bprm)
* default mmap base, as well as whatever program they
* might try to exec. This is because the brk will
* follow the loader, and is not movable. */
#ifdef CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE
/* Memory randomization might have been switched off
* in runtime via sysctl or explicit setting of
* personality flags.
* If that is the case, retain the original non-zero
* load_bias value in order to establish proper
* non-randomized mappings.
*/
load_bias = ELF_ET_DYN_BASE - vaddr;
if (current->flags & PF_RANDOMIZE)
load_bias = 0;
else
load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
#else
load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
#endif
load_bias += arch_mmap_rnd();
load_bias = ELF_PAGESTART(load_bias);
total_size = total_mapping_size(elf_phdata,
loc->elf_ex.e_phnum);
if (!total_size) {