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

Pull two overlayfs fixes from Miklos Szeredi:
 "Overlayfs rmdir() failed to check for emptiness in one case; this was
  introduced in 4.0.  The other bug was there since day one: failure to
  mount if upper fs is full, which bit some OpenWRT folks"

* 'overlayfs-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: mount read-only if workdir can't be created
  ovl: don't remove non-empty opaque directory

fs/overlayfs/copy_up.c

@@ -299,6 +299,9 @@ int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 	struct cred *override_cred;
 	char *link = NULL;
 
+	if (WARN_ON(!workdir))
+		return -EROFS;
+
 	ovl_path_upper(parent, &parentpath);
 	upperdir = parentpath.dentry;
 

fs/overlayfs/dir.c

@@ -222,6 +222,9 @@ static struct dentry *ovl_clear_empty(struct dentry *dentry,
 	struct kstat stat;
 	int err;
 
+	if (WARN_ON(!workdir))
+		return ERR_PTR(-EROFS);
+
 	err = ovl_lock_rename_workdir(workdir, upperdir);
 	if (err)
 		goto out;
@@ -322,6 +325,9 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 	struct dentry *newdentry;
 	int err;
 
+	if (WARN_ON(!workdir))
+		return -EROFS;
+
 	err = ovl_lock_rename_workdir(workdir, upperdir);
 	if (err)
 		goto out;
@@ -506,11 +512,28 @@ static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
 	struct dentry *opaquedir = NULL;
 	int err;
 
-	if (is_dir && OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
+	if (WARN_ON(!workdir))
+		return -EROFS;
+
+	if (is_dir) {
+		if (OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
 			opaquedir = ovl_check_empty_and_clear(dentry);
 			err = PTR_ERR(opaquedir);
 			if (IS_ERR(opaquedir))
 				goto out;
+		} else {
+			LIST_HEAD(list);
+
+			/*
+			 * When removing an empty opaque directory, then it
+			 * makes no sense to replace it with an exact replica of
+			 * itself.  But emptiness still needs to be checked.
+			 */
+			err = ovl_check_empty_dir(dentry, &list);
+			ovl_cache_free(&list);
+			if (err)
+				goto out;
+		}
 	}
 
 	err = ovl_lock_rename_workdir(workdir, upperdir);

fs/overlayfs/super.c

@@ -529,7 +529,7 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct ovl_fs *ufs = sb->s_fs_info;
 
-	if (!(*flags & MS_RDONLY) && !ufs->upper_mnt)
+	if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
 		return -EROFS;
 
 	return 0;
@@ -925,9 +925,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 		ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
 		err = PTR_ERR(ufs->workdir);
 		if (IS_ERR(ufs->workdir)) {
-			pr_err("overlayfs: failed to create directory %s/%s\n",
-			       ufs->config.workdir, OVL_WORKDIR_NAME);
-			goto out_put_upper_mnt;
+			pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
+				ufs->config.workdir, OVL_WORKDIR_NAME, -err);
+			sb->s_flags |= MS_RDONLY;
+			ufs->workdir = NULL;
 		}
 	}
 
@@ -997,7 +998,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	kfree(ufs->lower_mnt);
 out_put_workdir:
 	dput(ufs->workdir);
-out_put_upper_mnt:
 	mntput(ufs->upper_mnt);
 out_put_lowerpath:
 	for (i = 0; i < numlower; i++)