The patch titled
Subject: arm: factor out mmap ASLR into mmap_rnd
has been added to the -mm tree. Its filename is
arm-factor-out-mmap-aslr-into-mmap_rnd.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/arm-factor-out-mmap-aslr-into-mmap_rnd.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/arm-factor-out-mmap-aslr-into-mmap_rnd.patch
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------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: arm: factor out mmap ASLR into mmap_rnd
This separates ET_DYN ASLR from mmap ASLR, as already done on s390. The
various architectures that are already randomizing mmap (arm, arm64, mips,
powerpc, s390, and x86), have their various forms of arch_mmap_rnd() made
available via the new CONFIG_ARCH_HAS_ELF_RANDOMIZE. For these
architectures, arch_randomize_brk() is collapsed as well.
To address the "offset2lib" ASLR weakness[1], this separates ET_DYN ASLR
from mmap ASLR, as already done on s390. The architectures that are
already randomizing mmap (arm, arm64, mips, powerpc, s390, and x86), have
their various forms of arch_mmap_rnd() made available via the new
CONFIG_ARCH_HAS_ELF_RANDOMIZE. For these architectures,
arch_randomize_brk() is collapsed as well.
This is an alternative to the solutions in
https://lkml.org/lkml/2015/2/23/442
[1] http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html
This patch (of 5):
Move logic for mmap ASLR into separate function.
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Hector Marco-Gisbert <hecmargi@xxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: "David A. Long" <dave.long@xxxxxxxxxx>
Cc: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
Cc: Arun Chandran <achandran@xxxxxxxxxx>
Cc: Yann Droneaud <ydroneaud@xxxxxxxxxx>
Cc: Min-Hua Chen <orca.chen@xxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxxxx>
Cc: Alex Smith <alex@xxxxxxxxxxxxxxxx>
Cc: Markos Chandras <markos.chandras@xxxxxxxxxx>
Cc: Vineeth Vijayan <vvijayan@xxxxxxxxxx>
Cc: Jeff Bailey <jeffbailey@xxxxxxxxxx>
Cc: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx>
Cc: Ismael Ripoll <iripoll@xxxxxx>
Cc: Jan-Simon Mller <dl9pf@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm/mm/mmap.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff -puN arch/arm/mm/mmap.c~arm-factor-out-mmap-aslr-into-mmap_rnd arch/arm/mm/mmap.c
--- a/arch/arm/mm/mmap.c~arm-factor-out-mmap-aslr-into-mmap_rnd
+++ a/arch/arm/mm/mmap.c
@@ -169,14 +169,21 @@ arch_get_unmapped_area_topdown(struct fi
return addr;
}
-void arch_pick_mmap_layout(struct mm_struct *mm)
+static unsigned long mmap_rnd(void)
{
- unsigned long random_factor = 0UL;
+ unsigned long rnd = 0UL;
/* 8 bits of randomness in 20 address space bits */
if ((current->flags & PF_RANDOMIZE) &&
!(current->personality & ADDR_NO_RANDOMIZE))
- random_factor = (get_random_int() % (1 << 8)) << PAGE_SHIFT;
+ rnd = (get_random_int() % (1 << 8)) << PAGE_SHIFT;
+
+ return rnd;
+}
+
+void arch_pick_mmap_layout(struct mm_struct *mm)
+{
+ unsigned long random_factor = mmap_rnd();
if (mmap_is_legacy()) {
mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
arm-factor-out-mmap-aslr-into-mmap_rnd.patch
mm-expose-arch_mmap_rnd-when-available.patch
mm-move-randomize_et_dyn-into-elf_et_dyn_base.patch
mm-split-et_dyn-aslr-from-mmap-aslr.patch
mm-fold-arch_randomize_brk-into-arch_has_elf_randomize.patch
lib-vsprintf-add-%pt-format-specifier.patch
linux-next.patch
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