[S390] mmap: consider stack address randomization
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>
diff --git a/arch/s390/include/asm/elf.h b/arch/s390/include/asm/elf.h
index 354d426..9dbd3e7 100644
--- a/arch/s390/include/asm/elf.h
+++ b/arch/s390/include/asm/elf.h
@@ -206,6 +206,8 @@
current->mm->context.noexec == 0; \
})
+#define STACK_RND_MASK 0x7ffUL
+
#define ARCH_DLINFO \
do { \
if (vdso_enabled) \
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 869efba..5578740 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -30,6 +30,15 @@
#include <asm/pgalloc.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).
*
@@ -47,7 +56,7 @@
else if (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)