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Commit d1fd836d authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
Browse files

mm: split ET_DYN ASLR from mmap ASLR 

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: default avatarKees Cook <keescook@chromium.org>
Reported-by: default avatarHector Marco-Gisbert <hecmargi@upv.es>
Cc: Russell King <linux@arm.linux.org.uk>
Reviewed-by: default avatarIngo 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c6f5b001

arch/arm/Kconfig

+0 −1
Original line number Diff line number Diff line 
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

arch/arm64/Kconfig

+0 −1
Original line number Diff line number Diff line 
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

arch/mips/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/powerpc/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/s390/include/asm/elf.h

+2 −3
Original line number Diff line number Diff line
@@ -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. */