selinux: implement mmap on /selinux/policy
/selinux/policy allows a user to copy the policy back out of the kernel.
This patch allows userspace to actually mmap that file and use it directly.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 8eb102c..87e0556 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -439,9 +439,53 @@
return ret;
}
+static int sel_mmap_policy_fault(struct vm_area_struct *vma,
+ struct vm_fault *vmf)
+{
+ struct policy_load_memory *plm = vma->vm_file->private_data;
+ unsigned long offset;
+ struct page *page;
+
+ if (vmf->flags & (FAULT_FLAG_MKWRITE | FAULT_FLAG_WRITE))
+ return VM_FAULT_SIGBUS;
+
+ offset = vmf->pgoff << PAGE_SHIFT;
+ if (offset >= roundup(plm->len, PAGE_SIZE))
+ return VM_FAULT_SIGBUS;
+
+ page = vmalloc_to_page(plm->data + offset);
+ get_page(page);
+
+ vmf->page = page;
+
+ return 0;
+}
+
+static struct vm_operations_struct sel_mmap_policy_ops = {
+ .fault = sel_mmap_policy_fault,
+ .page_mkwrite = sel_mmap_policy_fault,
+};
+
+int sel_mmap_policy(struct file *filp, struct vm_area_struct *vma)
+{
+ if (vma->vm_flags & VM_SHARED) {
+ /* do not allow mprotect to make mapping writable */
+ vma->vm_flags &= ~VM_MAYWRITE;
+
+ if (vma->vm_flags & VM_WRITE)
+ return -EACCES;
+ }
+
+ vma->vm_flags |= VM_RESERVED;
+ vma->vm_ops = &sel_mmap_policy_ops;
+
+ return 0;
+}
+
static const struct file_operations sel_policy_ops = {
.open = sel_open_policy,
.read = sel_read_policy,
+ .mmap = sel_mmap_policy,
.release = sel_release_policy,
};