2 files changed, 13 insertions, 4 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 4349113881fb..537893a16014 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -500,17 +500,22 @@ out:
 #define INTERPRETER_AOUT 1
 #define INTERPRETER_ELF 2
 
+#ifndef STACK_RND_MASK
+#define STACK_RND_MASK 0x7ff            /* with 4K pages 8MB of VA */
+#endif
 
 static unsigned long randomize_stack_top(unsigned long stack_top)
 {
         unsigned int random_variable = 0;
 
-        if (current->flags & PF_RANDOMIZE)
-                random_variable = get_random_int() % (8*1024*1024);
+        if (current->flags & PF_RANDOMIZE) {
+                random_variable = get_random_int() & STACK_RND_MASK;
+                random_variable <<= PAGE_SHIFT;
+        }
 #ifdef CONFIG_STACK_GROWSUP
-        return PAGE_ALIGN(stack_top + random_variable);
+        return PAGE_ALIGN(stack_top) + random_variable;
 #else
-        return PAGE_ALIGN(stack_top - random_variable);
+        return PAGE_ALIGN(stack_top) - random_variable;
 #endif
 }
 
diff --git a/include/asm-x86_64/elf.h b/include/asm-x86_64/elf.h
index 43862cd6a569..c98633af07d2 100644
--- a/include/asm-x86_64/elf.h
+++ b/include/asm-x86_64/elf.h
@@ -8,6 +8,7 @@
 #include <asm/ptrace.h>
 #include <asm/user.h>
 #include <asm/processor.h>
+#include <asm/compat.h>
 
 /* x86-64 relocation types */
 #define R_X86_64_NONE           0       /* No reloc */
@@ -157,6 +158,9 @@ extern int dump_task_fpu (struct task_struct *, elf_fpregset_t *);
 #define ELF_CORE_COPY_TASK_REGS(tsk, elf_regs) dump_task_regs(tsk, elf_regs)
 #define ELF_CORE_COPY_FPREGS(tsk, elf_fpregs) dump_task_fpu(tsk, elf_fpregs)
 
+/* 1GB for 64bit, 8MB for 32bit */
+#define STACK_RND_MASK (is_compat_task() ? 0x7ff : 0x3fffff)
+
 #endif
 
 #endif