security: protect from stack expantion into low vm addresses
Add security checks to make sure we are not attempting to expand the
stack into memory protected by mmap_min_addr
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/mm/mmap.c b/mm/mmap.c
index facc1a7..938313c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1615,6 +1615,12 @@
*/
if (unlikely(anon_vma_prepare(vma)))
return -ENOMEM;
+
+ address &= PAGE_MASK;
+ error = security_file_mmap(0, 0, 0, 0, address, 1);
+ if (error)
+ return error;
+
anon_vma_lock(vma);
/*
@@ -1622,8 +1628,6 @@
* is required to hold the mmap_sem in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
*/
- address &= PAGE_MASK;
- error = 0;
/* Somebody else might have raced and expanded it already */
if (address < vma->vm_start) {
