1 files changed, 25 insertions, 12 deletions

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index c4feb89ad1e3..8c0a3d876fef 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -159,7 +159,8 @@ kill_whiteout:
 }
 
 struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
-			       struct dentry *newdentry, struct ovl_cattr *attr)
+			       struct dentry *newdentry, struct qstr *qname,
+			       struct ovl_cattr *attr)
 {
 	struct inode *dir = parent->d_inode;
 	int err;
@@ -221,19 +222,30 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
 		struct dentry *d;
 		/*
 		 * Some filesystems (i.e. casefolded) may return an unhashed
-		 * negative dentry from the ovl_lookup_upper() call before
+		 * negative dentry from the ovl_start_creating_upper() call before
 		 * ovl_create_real().
 		 * In that case, lookup again after making the newdentry
 		 * positive, so ovl_create_upper() always returns a hashed
-		 * positive dentry.
+		 * positive dentry.  We lookup using qname which should be
+		 * the same name as newentry, but is certain not to change.
+		 * As we have to drop the lock before the lookup a race
+		 * could result in a lookup failure.  In that case we return
+		 * an error.
 		 */
-		d = ovl_lookup_upper(ofs, newdentry->d_name.name, parent,
-				     newdentry->d_name.len);
-		dput(newdentry);
-		if (IS_ERR_OR_NULL(d))
+		end_creating_keep(newdentry);
+		d = ovl_start_creating_upper(ofs, parent, qname);
+
+		if (IS_ERR_OR_NULL(d)) {
 			err = d ? PTR_ERR(d) : -ENOENT;
-		else
+		} else if (d->d_inode != newdentry->d_inode) {
+			err = -EIO;
+		} else {
+			dput(newdentry);
 			return d;
+		}
+		end_creating(d);
+		dput(newdentry);
+		return ERR_PTR(err);
 	}
 out:
 	if (err) {
@@ -252,7 +264,7 @@ struct dentry *ovl_create_temp(struct ovl_fs *ofs, struct dentry *workdir,
 	ret = ovl_start_creating_temp(ofs, workdir, name);
 	if (IS_ERR(ret))
 		return ret;
-	ret = ovl_create_real(ofs, workdir, ret, attr);
+	ret = ovl_create_real(ofs, workdir, ret, &QSTR(name), attr);
 	return end_creating_keep(ret);
 }
 
@@ -352,14 +364,15 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 	struct dentry *newdentry;
+	struct qstr qname = QSTR_LEN(dentry->d_name.name,
+				     dentry->d_name.len);
 	int err;
 
 	newdentry = ovl_start_creating_upper(ofs, upperdir,
-					     &QSTR_LEN(dentry->d_name.name,
-						       dentry->d_name.len));
+					     &qname);
 	if (IS_ERR(newdentry))
 		return PTR_ERR(newdentry);
-	newdentry = ovl_create_real(ofs, upperdir, newdentry, attr);
+	newdentry = ovl_create_real(ofs, upperdir, newdentry, &qname, attr);
 	if (IS_ERR(newdentry))
 		return PTR_ERR(newdentry);