mm/shmem.c: zero out unused vma fields in shmem_pseudo_vma_init()

shmem/tmpfs uses pseudo vma to allocate page with correct NUMA policy.

The pseudo vma doesn't have vm_page_prot set.  We are going to encode
encryption KeyID in vm_page_prot.  Having garbage there causes problems.

Zero out all unused fields in the pseudo vma.

Link: http://lkml.kernel.org/r/20180531135602.20321-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index 2b686e3..e9a7ac7 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1420,10 +1420,9 @@ static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
                struct shmem_inode_info *info, pgoff_t index)
 {
        /* Create a pseudo vma that just contains the policy */
-       vma->vm_start = 0;
+       memset(vma, 0, sizeof(*vma));
        /* Bias interleave by inode number to distribute better across nodes */
        vma->vm_pgoff = index + info->vfs_inode.i_ino;
-       vma->vm_ops = NULL;
        vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 }