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s390/mmap: take stack_guard_gap into account for mmap_base

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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: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2019-01-29 10:48:09 +01:00
parent d4192437d7
commit a0308c1315
1 changed files with 19 additions and 14 deletions
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33
arch/s390/mm/mmap.c
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@ -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;
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;
/* 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;
return PAGE_ALIGN(STACK_TOP - gap - rnd);
}
unsigned long