[patch 080/118] mm/shmem.c: zero out unused vma fields in shmem_pseudo_vma_init()

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From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/shmem.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff -puN mm/shmem.c~mm-shmem-zero-out-unused-vma-fields-in-shmem_pseudo_vma_init mm/shmem.c
--- a/mm/shmem.c~mm-shmem-zero-out-unused-vma-fields-in-shmem_pseudo_vma_init
+++ a/mm/shmem.c
@@ -1420,10 +1420,9 @@ static void shmem_pseudo_vma_init(struct
 		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);
 }
 
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