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Commit 912f9ee2 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
Browse files

powerpc: Randomise the brk region 



Randomize the heap.

before:
tundro2:~ # sleep 1 & cat /proc/${!}/maps | grep heap
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]

after
tundro2:~ # sleep 1 & cat /proc/${!}/maps | grep heap
19419000-1951a000 rw-p 19419000 00:00 0                                  [heap]
325ff000-32700000 rw-p 325ff000 00:00 0                                  [heap]
1a97c000-1aa7d000 rw-p 1a97c000 00:00 0                                  [heap]
1cc60000-1cd61000 rw-p 1cc60000 00:00 0                                  [heap]
1afa9000-1b0aa000 rw-p 1afa9000 00:00 0                                  [heap]

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent d839088c

arch/powerpc/include/asm/elf.h

+3 −0
Original line number Diff line number Diff line
@@ -276,6 +276,9 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm, 
	(0x7ff >> (PAGE_SHIFT - 12)) : \

	(0x3ffff >> (PAGE_SHIFT - 12)))



extern unsigned long arch_randomize_brk(struct mm_struct *mm);

#define arch_randomize_brk arch_randomize_brk



#endif /* __KERNEL__ */



/*

arch/powerpc/kernel/process.c

+23 −0
Original line number Diff line number Diff line
@@ -1147,3 +1147,26 @@ unsigned long arch_align_stack(unsigned long sp) 
		sp -= get_random_int() & ~PAGE_MASK;

	return sp & ~0xf;

}



static inline unsigned long brk_rnd(void)

{

        unsigned long rnd = 0;



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

	if (is_32bit_task())

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

	else

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



	return rnd << PAGE_SHIFT;

}



unsigned long arch_randomize_brk(struct mm_struct *mm)

{

	unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());



	if (ret < mm->brk)

		return mm->brk;



	return ret;

}