s390/mm: Fix crst upgrade of mmap with MAP_FIXED

Right now the page table upgrade does not happen if the end address
of a fixed mapping is greater than TASK_SIZE.
Enhance s390_mmap_check() to handle MAP_FIXED mappings correctly.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/mman.h

@@ -9,7 +9,7 @@
 #include <uapi/asm/mman.h>
 
 #if !defined(__ASSEMBLY__) && defined(CONFIG_64BIT)
-int s390_mmap_check(unsigned long addr, unsigned long len);
-#define arch_mmap_check(addr,len,flags)	s390_mmap_check(addr,len)
+int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags);
+#define arch_mmap_check(addr, len, flags) s390_mmap_check(addr, len, flags)
 #endif
 #endif /* __S390_MMAN_H__ */

arch/s390/mm/mmap.c

@@ -101,12 +101,15 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 
 #else
 
-int s390_mmap_check(unsigned long addr, unsigned long len)
+int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
 {
 	int rc;
 
-	if (!is_compat_task() &&
-	    len >= TASK_SIZE && TASK_SIZE < (1UL << 53)) {
+	if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
+		return 0;
+	if (!(flags & MAP_FIXED))
+		addr = 0;
+	if ((addr + len) >= TASK_SIZE) {
 		rc = crst_table_upgrade(current->mm, 1UL << 53);
 		if (rc)
 			return rc;