[PATCH v4 07/10] mm: expose arch_mmap_rnd when available

From: Kees Cook
Date: Wed Mar 04 2015 - 16:16:59 EST

When an architecture fully supports randomizing the ELF load location,
a per-arch mmap_rnd() function is used to find a randomized mmap base.
In preparation for randomizing the location of ET_DYN binaries
separately from mmap, this renames and exports these functions as
arch_mmap_rnd(). Additionally introduces CONFIG_ARCH_HAS_ELF_RANDOMIZE
for describing this feature on architectures that support it
(which is a superset of ARCH_BINFMT_ELF_RANDOMIZE_PIE, since s390
already supports a separated ET_DYN ASLR from mmap ASLR without the
ARCH_BINFMT_ELF_RANDOMIZE_PIE logic).

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
arch/Kconfig | 7 +++++++
arch/arm/Kconfig | 1 +
arch/arm/mm/mmap.c | 4 ++--
arch/arm64/Kconfig | 1 +
arch/arm64/mm/mmap.c | 4 ++--
arch/mips/Kconfig | 1 +
arch/mips/mm/mmap.c | 4 ++--
arch/powerpc/Kconfig | 1 +
arch/powerpc/mm/mmap.c | 4 ++--
arch/s390/Kconfig | 1 +
arch/s390/mm/mmap.c | 8 ++++----
arch/x86/Kconfig | 1 +
arch/x86/mm/mmap.c | 4 ++--
include/linux/elf-randomize.h | 10 ++++++++++
14 files changed, 37 insertions(+), 14 deletions(-)
create mode 100644 include/linux/elf-randomize.h

diff --git a/arch/Kconfig b/arch/Kconfig
index 05d7a8a458d5..9ff5aa8fa2c1 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -484,6 +484,13 @@ config HAVE_IRQ_EXIT_ON_IRQ_STACK
This spares a stack switch and improves cache usage on softirq
processing.

+config ARCH_HAS_ELF_RANDOMIZE
+ bool
+ help
+ An architecture supports choosing randomized locations for
+ stack, mmap, brk, and ET_DYN. Defined functions:
+ - arch_mmap_rnd()
+
#
# ABI hall of shame
#
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9f1f09a2bc9b..248d99cabaa8 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -3,6 +3,7 @@ config ARM
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
select ARCH_HAVE_CUSTOM_GPIO_H
select ARCH_HAS_GCOV_PROFILE_ALL
diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 15a8160096b3..407dc786583a 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -169,7 +169,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
return addr;
}

-static unsigned long mmap_rnd(void)
+unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;

@@ -184,7 +184,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
unsigned long random_factor = 0UL;

if (current->flags & PF_RANDOMIZE)
- random_factor = mmap_rnd();
+ random_factor = arch_mmap_rnd();

if (mmap_is_legacy()) {
mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1b8e97331ffb..5f469095e0e2 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2,6 +2,7 @@ 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
select ARCH_HAS_SG_CHAIN
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index ba776c01b552..ed177475dd8c 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -47,7 +47,7 @@ static int mmap_is_legacy(void)
return sysctl_legacy_va_layout;
}

-static unsigned long mmap_rnd(void)
+unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;

@@ -77,7 +77,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
unsigned long random_factor = 0UL;

if (current->flags & PF_RANDOMIZE)
- random_factor = mmap_rnd();
+ random_factor = arch_mmap_rnd();

/*
* Fall back to the standard layout if the personality bit is set, or
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index c7a16904cd03..72ce5cece768 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -24,6 +24,7 @@ config MIPS
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
select GENERIC_ATOMIC64 if !64BIT
diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index 9a4f1f5c1f0e..5c81fdd032c3 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -142,7 +142,7 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
addr0, len, pgoff, flags, DOWN);
}

-static unsigned long mmap_rnd(void)
+unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;

@@ -161,7 +161,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
unsigned long random_factor = 0UL;

if (current->flags & PF_RANDOMIZE)
- random_factor = mmap_rnd();
+ random_factor = arch_mmap_rnd();

if (mmap_is_legacy()) {
mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 22b0940494bb..14fe1c411489 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -89,6 +89,7 @@ config PPC
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
select OF_RESERVED_MEM
diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index 1ad2299d795d..0f0502e12f6c 100644
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c
@@ -53,7 +53,7 @@ static inline int mmap_is_legacy(void)
return sysctl_legacy_va_layout;
}

-static unsigned long mmap_rnd(void)
+unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;

@@ -87,7 +87,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
unsigned long random_factor = 0UL;

if (current->flags & PF_RANDOMIZE)
- random_factor = mmap_rnd();
+ random_factor = arch_mmap_rnd();

/*
* Fall back to the standard layout if the personality
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 373cd5badf1c..4d707bb3e8dd 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -65,6 +65,7 @@ config S390
def_bool y
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
+ select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_SG_CHAIN
select ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index db57078075c5..a94504d99c47 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -60,7 +60,7 @@ static inline int mmap_is_legacy(void)
return sysctl_legacy_va_layout;
}

-static unsigned long mmap_rnd(void)
+unsigned long arch_mmap_rnd(void)
{
if (is_32bit_task())
return (get_random_int() & 0x7ff) << PAGE_SHIFT;
@@ -187,7 +187,7 @@ unsigned long randomize_et_dyn(void)
base &= ~((1UL << 32) - 1);

if (current->flags & PF_RANDOMIZE)
- base += mmap_rnd();
+ base += arch_mmap_rnd();

return base;
}
@@ -203,7 +203,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
unsigned long random_factor = 0UL;

if (current->flags & PF_RANDOMIZE)
- random_factor = mmap_rnd();
+ random_factor = arch_mmap_rnd();

/*
* Fall back to the standard layout if the personality
@@ -283,7 +283,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
unsigned long random_factor = 0UL;

if (current->flags & PF_RANDOMIZE)
- random_factor = mmap_rnd();
+ random_factor = arch_mmap_rnd();

/*
* Fall back to the standard layout if the personality
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c2fb8a87dccb..9aa91727fbf8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -88,6 +88,7 @@ config X86
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
select SPARSE_IRQ
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index ebfa52030d5c..9d518d693b4b 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -65,7 +65,7 @@ static int mmap_is_legacy(void)
return sysctl_legacy_va_layout;
}

-static unsigned long mmap_rnd(void)
+unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;

@@ -114,7 +114,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
unsigned long random_factor = 0UL;

if (current->flags & PF_RANDOMIZE)
- random_factor = mmap_rnd();
+ random_factor = arch_mmap_rnd();

mm->mmap_legacy_base = mmap_legacy_base(random_factor);

diff --git a/include/linux/elf-randomize.h b/include/linux/elf-randomize.h
new file mode 100644
index 000000000000..7a4eda02d2b1
--- /dev/null
+++ b/include/linux/elf-randomize.h
@@ -0,0 +1,10 @@
+#ifndef _ELF_RANDOMIZE_H
+#define _ELF_RANDOMIZE_H
+
+#ifndef CONFIG_ARCH_HAS_ELF_RANDOMIZE
+static inline unsigned long arch_mmap_rnd(void) { return 0; }
+#else
+extern unsigned long arch_mmap_rnd(void);
+#endif
+
+#endif
--
1.9.1

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