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[S390] mmap: consider stack address randomization

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Consider stack address randomization when calulating mmap_base for
flexible mmap layout . Because of address randomization the stack
address can be up to 8MB lower than STACK_TOP.
When calculating mmap_base this isn't taken into account, which could
lead to the case that the gap between the real stack top and mmap_base
is lower than what ulimit specifies for the maximum stack size.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2011-01-12 09:55:22 +01:00 committed by Martin Schwidefsky
parent 7a63fa1a85
commit 9046e401e7
2 changed files with 12 additions and 1 deletions
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2
arch/s390/include/asm/elf.h
View File

@ -206,6 +206,8 @@ do { \
current->mm->context.noexec == 0; \ current->mm->context.noexec == 0; \
}) })
#define STACK_RND_MASK 0x7ffUL
#define ARCH_DLINFO \ #define ARCH_DLINFO \
do { \ do { \
if (vdso_enabled) \ if (vdso_enabled) \

11
arch/s390/mm/mmap.c
View File

@ -30,6 +30,15 @@
#include <asm/pgalloc.h> #include <asm/pgalloc.h>
#include <asm/compat.h> #include <asm/compat.h>
static unsigned long stack_maxrandom_size(void)
{
if (!(current->flags & PF_RANDOMIZE))
return 0;
if (current->personality & ADDR_NO_RANDOMIZE)
return 0;
return STACK_RND_MASK << PAGE_SHIFT;
}
/* /*
* Top of mmap area (just below the process stack). * Top of mmap area (just below the process stack).
* *
@ -47,7 +56,7 @@ static inline unsigned long mmap_base(void)
else if (gap > MAX_GAP) else if (gap > MAX_GAP)
gap = MAX_GAP; gap = MAX_GAP;
return STACK_TOP - (gap & PAGE_MASK); return STACK_TOP - stack_maxrandom_size() - (gap & PAGE_MASK);
} }
static inline int mmap_is_legacy(void) static inline int mmap_is_legacy(void)