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Commit df1ca53c authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
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[S390] Randomize mmap start address 



Randomize mmap start address with 8MB.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 1060f62e

arch/s390/mm/mmap.c

+11 −2
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <linux/personality.h>

#include <linux/mm.h>

#include <linux/module.h>

#include <linux/random.h>

#include <asm/pgalloc.h>

#include <asm/compat.h>
@@ -56,6 +57,14 @@ static inline int mmap_is_legacy(void) 
	return sysctl_legacy_va_layout;

}



static unsigned long mmap_rnd(void)

{

	if (!(current->flags & PF_RANDOMIZE))

		return 0;

	/* 8MB randomization for mmap_base */

	return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;

}



static inline unsigned long mmap_base(void)

{

	unsigned long gap = rlimit(RLIMIT_STACK);
@@ -64,8 +73,8 @@ static inline unsigned long mmap_base(void) 
		gap = MIN_GAP;

	else if (gap > MAX_GAP)

		gap = MAX_GAP;



	return STACK_TOP - stack_maxrandom_size() - (gap & PAGE_MASK);

	gap &= PAGE_MASK;

	return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;

}



#ifndef CONFIG_64BIT