Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:
 "This fixes d_ino correctness in readdir, which brings overlayfs on par
  with normal filesystems regarding inode number semantics, as long as
  all layers are on the same filesystem.

  There are also some bug fixes, one in particular (random ioctl's
  shouldn't be able to modify lower layers) that touches some vfs code,
  but of course no-op for non-overlay fs"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fix false positive ESTALE on lookup
  ovl: don't allow writing ioctl on lower layer
  ovl: fix relatime for directories
  vfs: add flags to d_real()
  ovl: cleanup d_real for negative
  ovl: constant d_ino for non-merge dirs
  ovl: constant d_ino across copy up
  ovl: fix readdir error value
  ovl: check snprintf return

1 files changed, 10 insertions, 4 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 5bc71642b226..a619addecafc 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -498,6 +498,9 @@ static int ovl_set_nlink_common(struct dentry *dentry,
 	len = snprintf(buf, sizeof(buf), format,
 		       (int) (inode->i_nlink - realinode->i_nlink));
 
+	if (WARN_ON(len >= sizeof(buf)))
+		return -EIO;
+
 	return ovl_do_setxattr(ovl_dentry_upper(dentry),
 			       OVL_XATTR_NLINK, buf, len, 0);
 }
@@ -576,10 +579,13 @@ static int ovl_inode_set(struct inode *inode, void *data)
 static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
 			     struct dentry *upperdentry)
 {
-	struct inode *lowerinode = lowerdentry ? d_inode(lowerdentry) : NULL;
-
-	/* Lower (origin) inode must match, even if NULL */
-	if (ovl_inode_lower(inode) != lowerinode)
+	/*
+	 * Allow non-NULL lower inode in ovl_inode even if lowerdentry is NULL.
+	 * This happens when finding a copied up overlay inode for a renamed
+	 * or hardlinked overlay dentry and lower dentry cannot be followed
+	 * by origin because lower fs does not support file handles.
+	 */
+	if (lowerdentry && ovl_inode_lower(inode) != d_inode(lowerdentry))
 		return false;
 
 	/*