Commit a0308c13 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/mmap: take stack_guard_gap into account for mmap_base 



The s390 version of the mmap_base function is ignorant of stack_guard_gap
which can lead to a placement of the stack vs. the mmap base that does not
leave enough space for the stack rlimit.

Add the stack_guard_gap to the calculation and while we are at it the
check for gap+pad overflows as well.

Reviewed-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent d4192437

arch/s390/mm/mmap.c

+19 −14
Original line number Diff line number Diff line
@@ -29,14 +29,6 @@ static unsigned long stack_maxrandom_size(void) 
	return STACK_RND_MASK << PAGE_SHIFT;

}



/*

 * Top of mmap area (just below the process stack).

 *

 * Leave at least a ~32 MB hole.

 */

#define MIN_GAP (32*1024*1024)

#define MAX_GAP (STACK_TOP/6*5)



static inline int mmap_is_legacy(struct rlimit *rlim_stack)

{

	if (current->personality & ADDR_COMPAT_LAYOUT)
@@ -60,13 +52,26 @@ static inline unsigned long mmap_base(unsigned long rnd, 
				      struct rlimit *rlim_stack)

{

	unsigned long gap = rlim_stack->rlim_cur;

	unsigned long pad = stack_maxrandom_size() + stack_guard_gap;

	unsigned long gap_min, gap_max;



	/* Values close to RLIM_INFINITY can overflow. */

	if (gap + pad > gap)

		gap += pad;



	/*

	 * Top of mmap area (just below the process stack).

	 * Leave at least a ~32 MB hole.

	 */

	gap_min = 32 * 1024 * 1024UL;

	gap_max = (STACK_TOP / 6) * 5;



	if (gap < gap_min)

		gap = gap_min;

	else if (gap > gap_max)

		gap = gap_max;



	if (gap < MIN_GAP)

		gap = MIN_GAP;

	else if (gap > MAX_GAP)

		gap = MAX_GAP;

	gap &= PAGE_MASK;

	return STACK_TOP - stack_maxrandom_size() - rnd - gap;

	return PAGE_ALIGN(STACK_TOP - gap - rnd);

}



unsigned long

CRA Git | Maintained and supported by SUSTech CRA and CCSE