s390/mm: downgrade page table after fork of a 31 bit process
The downgrade of the 4 level page table created by init_new_context is
currently done only in start_thread31. If a 31 bit process forks the
new mm uses a 4 level page table, including the task size of 2<<42
that goes along with it. This is incorrect as now a 31 bit process
can map memory beyond 2GB. Define arch_dup_mmap to do the downgrade
after fork.
Cc: stable@vger.kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 5733842..c59a5ef 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -103,9 +103,15 @@
int s390_mmap_check(unsigned long addr, unsigned long len)
{
+ int rc;
+
if (!is_compat_task() &&
- len >= TASK_SIZE && TASK_SIZE < (1UL << 53))
- return crst_table_upgrade(current->mm, 1UL << 53);
+ len >= TASK_SIZE && TASK_SIZE < (1UL << 53)) {
+ rc = crst_table_upgrade(current->mm, 1UL << 53);
+ if (rc)
+ return rc;
+ update_mm(current->mm, current);
+ }
return 0;
}
@@ -125,6 +131,7 @@
rc = crst_table_upgrade(mm, 1UL << 53);
if (rc)
return (unsigned long) rc;
+ update_mm(mm, current);
area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
}
return area;
@@ -147,6 +154,7 @@
rc = crst_table_upgrade(mm, 1UL << 53);
if (rc)
return (unsigned long) rc;
+ update_mm(mm, current);
area = arch_get_unmapped_area_topdown(filp, addr, len,
pgoff, flags);
}