mm: expose arch_mmap_rnd when available

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@chromium.org>
Cc: 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>

14 files changed, 37 insertions, 14 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index c88c23f0a1da..474904a8e540 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -491,6 +491,13 @@ config PGTABLE_LEVELS
         int
         default 2
 
+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 696cf3c61e0f..f85200a63a8b 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 3f2fba996bc2..7c1dbeb73e8d 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 a9d112d2a135..688ce274f59d 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 91ad76f30d18..fc5fffbb331b 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 f6aebcb7a0f8..ac2b75d74cd2 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 0f948cefaeb1..782ddbbc1c9a 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