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Commit 332ec5e7 authored by Kees Cook's avatar Kees Cook Committed by Trilok Soni
Browse files

powerpc: 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.

(Can mmap ASLR be safely enabled in the legacy mmap case here?  Other
archs use "mm->mmap_base = TASK_UNMAPPED_BASE + random_factor".)

Change-Id: I8539fc2499c243019bfb279422618f6f235d783d
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Git-commit: ed6322746afb74c2509e2f3a6464182793b16eb9
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: default avatarSe Wang (Patrick) Oh <sewango@codeaurora.org>
parent cf0859d4

arch/powerpc/mm/mmap.c

+15 −11
Original line number Diff line number Diff line
@@ -55,19 +55,18 @@ static inline int mmap_is_legacy(void) 


static unsigned long mmap_rnd(void)

{

	unsigned long rnd = 0;

	unsigned long rnd;



	if (current->flags & PF_RANDOMIZE) {

	/* 8MB for 32bit, 1GB for 64bit */

	if (is_32bit_task())

			rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));

		rnd = (unsigned long)get_random_int() % (1<<(23-PAGE_SHIFT));

	else

			rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));

	}

		rnd = (unsigned long)get_random_int() % (1<<(30-PAGE_SHIFT));



	return rnd << PAGE_SHIFT;

}



static inline unsigned long mmap_base(void)

static inline unsigned long mmap_base(unsigned long rnd)

{

	unsigned long gap = rlimit(RLIMIT_STACK);
@@ -76,7 +75,7 @@ static inline unsigned long mmap_base(void) 
	else if (gap > MAX_GAP)

		gap = MAX_GAP;



	return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());

	return PAGE_ALIGN(TASK_SIZE - gap - rnd);

}



/*
@@ -85,6 +84,11 @@ static inline 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:
@@ -93,7 +97,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm) 
		mm->mmap_base = TASK_UNMAPPED_BASE;

		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;

	}

}