[PATCH 2/5] mm: expose arch_mmap_rnd when available

From: Kees Cook <hidden>
Date: 2015-03-03 00:19:45
Also in: linux-arm-kernel, linux-fsdevel, linux-mips, lkml
Subsystem: arm port, arm64 port (aarch64 architecture), exec & binfmt api, elf, filesystems (vfs and infrastructure), linux for powerpc (32-bit and 64-bit), mips, s390 architecture, the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers: Russell King, Catalin Marinas, Will Deacon, Kees Cook, Alexander Viro, Christian Brauner, Madhavan Srinivasan, Thomas Bogendoerfer, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra

When an architecture fully supports randomizing the ELF load location, a
per-arch mmap_rnd() function is used to finding 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 does this
witout the ARCH_BINFMT_ELF_RANDOMIZE_PIE logic).

Signed-off-by: Kees Cook <redacted>
---
 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           |  9 ++++++---
 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            |  6 +++---
 fs/binfmt_elf.c               |  1 +
 include/linux/elf-randomize.h | 10 ++++++++++
 15 files changed, 43 insertions(+), 16 deletions(-)
 create mode 100644 include/linux/elf-randomize.h

diff --git a/arch/Kconfig b/arch/Kconfig
index 05d7a8a458d5..e315cc79ebe7 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(), must respect (current->flags & PF_RANDOMIZE)
+
 #
 # 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 0f8bc158f2c6..3c1fedb034bb 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 = 0UL;

@@ -183,7 +183,7 @@ static unsigned long mmap_rnd(void)
 
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
-	unsigned long random_factor = mmap_rnd();
+	unsigned long 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 54922d1275b8..b7117cb4bc07 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 = 0;

@@ -66,7 +66,7 @@ static unsigned long mmap_base(void)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 
-	return PAGE_ALIGN(STACK_TOP - gap - mmap_rnd());
+	return PAGE_ALIGN(STACK_TOP - gap - arch_mmap_rnd());
 }
 
 /*

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 f1baadd56e82..d32490d99671 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c

@@ -164,9 +164,12 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 	}
 }
 
-static inline unsigned long brk_rnd(void)
+unsigned long arch_mmap_rnd(void)
 {
-	unsigned long rnd = get_random_int();
+	unsigned long rnd = 0;
+
+	if (current->flags & PF_RANDOMIZE)
+		rnd = get_random_int();
 
 	rnd = rnd << PAGE_SHIFT;
 	/* 8MB for 32bit, 256MB for 64bit */

@@ -183,7 +186,7 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
 	unsigned long base = mm->brk;
 	unsigned long ret;
 
-	ret = PAGE_ALIGN(base + brk_rnd());
+	ret = PAGE_ALIGN(base + arch_mmap_rnd());
 
 	if (ret < mm->brk)
 		return mm->brk;

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 cb8bdbe4972f..d1111b49f03d 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 = 0;

@@ -76,7 +76,7 @@ static inline unsigned long mmap_base(void)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 
-	return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
+	return PAGE_ALIGN(TASK_SIZE - gap - arch_mmap_rnd());
 }
 
 /*

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 179a2c20b01f..77759e35671b 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 (!(current->flags & PF_RANDOMIZE))
 		return 0;

@@ -72,7 +72,7 @@ static unsigned long mmap_rnd(void)
 
 static unsigned long mmap_base_legacy(void)
 {
-	return TASK_UNMAPPED_BASE + mmap_rnd();
+	return TASK_UNMAPPED_BASE + arch_mmap_rnd();
 }
 
 static inline unsigned long mmap_base(void)

@@ -84,7 +84,7 @@ static inline unsigned long mmap_base(void)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 	gap &= PAGE_MASK;
-	return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
+	return STACK_TOP - stack_maxrandom_size() - arch_mmap_rnd() - gap;
 }
 
 unsigned long

@@ -187,7 +187,7 @@ unsigned long randomize_et_dyn(void)
 	if (!is_32bit_task())
 		/* Align to 4GB */
 		base &= ~((1UL << 32) - 1);
-	return base + mmap_rnd();
+	return base + arch_mmap_rnd();
 }
 
 #ifndef CONFIG_64BIT

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 df4552bd239e..a65e2b3154da 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 = 0;

@@ -91,7 +91,7 @@ static unsigned long mmap_base(void)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 
-	return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
+	return PAGE_ALIGN(TASK_SIZE - gap - arch_mmap_rnd());
 }
 
 /*

@@ -103,7 +103,7 @@ static unsigned long mmap_legacy_base(void)
 	if (mmap_is_ia32())
 		return TASK_UNMAPPED_BASE;
 	else
-		return TASK_UNMAPPED_BASE + mmap_rnd();
+		return TASK_UNMAPPED_BASE + arch_mmap_rnd();
 }
 
 /*

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 995986b8e36b..b1c5ef5d9322 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c

@@ -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>

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

-- 
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