Commit dd04cff1 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
Browse files

arm64: standardize mmap_rnd() usage 



In preparation for splitting out ET_DYN ASLR, this refactors the use of
mmap_rnd() to be used similarly to arm and x86.  This additionally
enables mmap ASLR on legacy mmap layouts, which appeared to be missing
on arm64, and was already supported on arm.  Additionally removes a
copy/pasted declaration of an unused function.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 82168140

arch/arm64/include/asm/elf.h

+0 −1
Original line number Diff line number Diff line
@@ -125,7 +125,6 @@ typedef struct user_fpsimd_state elf_fpregset_t; 
 * the loader.  We need to make sure that it is out of the way of the program

 * 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	(2 * TASK_SIZE_64 / 3)



/*

arch/arm64/mm/mmap.c

+11 −7
Original line number Diff line number Diff line
@@ -49,15 +49,14 @@ static int mmap_is_legacy(void) 


static unsigned long mmap_rnd(void)

{

	unsigned long rnd = 0;

	unsigned long rnd;



	if (current->flags & PF_RANDOMIZE)

		rnd = (long)get_random_int() & STACK_RND_MASK;

	rnd = (unsigned long)get_random_int() & STACK_RND_MASK;



	return rnd << PAGE_SHIFT;

}



static unsigned long mmap_base(void)

static unsigned long mmap_base(unsigned long rnd)

{

	unsigned long gap = rlimit(RLIMIT_STACK);
@@ -66,7 +65,7 @@ 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 - rnd);

}



/*
@@ -75,15 +74,20 @@ static unsigned long mmap_base(void) 
 */

void arch_pick_mmap_layout(struct mm_struct *mm)

{

	unsigned long random_factor = 0UL;



	if (current->flags & PF_RANDOMIZE)

		random_factor = mmap_rnd();



	/*

	 * Fall back to the standard layout if the personality bit is set, or

	 * if the expected stack growth is unlimited:

	 */

	if (mmap_is_legacy()) {

		mm->mmap_base = TASK_UNMAPPED_BASE;

		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;

		mm->get_unmapped_area = arch_get_unmapped_area;

	} else {

		mm->mmap_base = mmap_base();

		mm->mmap_base = mmap_base(random_factor);

		mm->get_unmapped_area = arch_get_unmapped_area_topdown;

	}

}

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