arm64: ASLR: Don't randomise text when randomise_va_space == 0

When user asks to turn off ASLR by writing "0" to
/proc/sys/kernel/randomize_va_space there should not be
any randomization to mmap base, stack, VDSO, libs, text and heap

Currently arm64 violates this behavior by randomising text.
Fix this by defining a constant ELF_ET_DYN_BASE. The randomisation of
mm->mmap_base is done by setup_new_exec -> arch_pick_mmap_layout ->
mmap_base -> mmap_rnd.

Signed-off-by: Arun Chandran <achandran@mvista.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

3 files changed, 3 insertions, 7 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b8053be1d803..9532f8d5857e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1,5 +1,6 @@
 config ARM64
         def_bool y
+        select ARCH_BINFMT_ELF_RANDOMIZE_PIE
         select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
         select ARCH_HAS_SG_CHAIN
         select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 01d3aab64b79..1f65be393139 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -126,7 +126,7 @@ typedef struct user_fpsimd_state elf_fpregset_t;
  * that it will "exec", and that there is sufficient room for the brk.
  */
 extern unsigned long randomize_et_dyn(unsigned long base);
-#define ELF_ET_DYN_BASE (randomize_et_dyn(2 * TASK_SIZE_64 / 3))
+#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3)
 
 /*
  * When the program starts, a1 contains a pointer to a function to be
@@ -169,7 +169,7 @@ extern unsigned long arch_randomize_brk(struct mm_struct *mm);
 #define COMPAT_ELF_PLATFORM             ("v8l")
 #endif
 
-#define COMPAT_ELF_ET_DYN_BASE          (randomize_et_dyn(2 * TASK_SIZE_32 / 3))
+#define COMPAT_ELF_ET_DYN_BASE          (2 * TASK_SIZE_32 / 3)
 
 /* AArch32 registers. */
 #define COMPAT_ELF_NGREG                18
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index c3065dbc4fa2..fde9923af859 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -378,8 +378,3 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
         return randomize_base(mm->brk);
 }
-
-unsigned long randomize_et_dyn(unsigned long base)
-{
-        return randomize_base(base);
-}