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Commit 6ae53cd4 authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
Browse files

[PATCH] x86_64: Fix stack/mmap randomization for compat tasks 



ia32_setup_arg_pages would ignore the passed in random stack top
and use its own static value.

Now it uses the 8bit of randomness native i386 would use too.

This indirectly fixes mmap randomization for 32bit processes too,
which depends on the stack randomization.

Should also give slightly better virtual cache colouring and
possibly better performance with HyperThreading.

Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 3793c65c

arch/x86_64/ia32/ia32_binfmt.c

+2 −2
Original line number Diff line number Diff line
@@ -339,7 +339,7 @@ int ia32_setup_arg_pages(struct linux_binprm *bprm, unsigned long stack_top, 
	struct mm_struct *mm = current->mm;

	int i, ret;



	stack_base = IA32_STACK_TOP - MAX_ARG_PAGES * PAGE_SIZE;

	stack_base = stack_top - MAX_ARG_PAGES * PAGE_SIZE;

	mm->arg_start = bprm->p + stack_base;



	bprm->p += stack_base;
@@ -357,7 +357,7 @@ int ia32_setup_arg_pages(struct linux_binprm *bprm, unsigned long stack_top, 
	{

		mpnt->vm_mm = mm;

		mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;

		mpnt->vm_end = IA32_STACK_TOP;

		mpnt->vm_end = stack_top;

		if (executable_stack == EXSTACK_ENABLE_X)

			mpnt->vm_flags = VM_STACK_FLAGS |  VM_EXEC;

		else if (executable_stack == EXSTACK_DISABLE_X)

include/asm-x86_64/elf.h

+1 −1
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ extern int dump_task_fpu (struct task_struct *, elf_fpregset_t *); 
#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)

#define STACK_RND_MASK (test_thread_flag(TIF_IA32) ? 0x7ff : 0x3fffff)



#endif