Patch "ovl: do not cleanup unsupported index entries" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

ovl: do not cleanup unsupported index entries

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ovl-do-not-cleanup-unsupported-index-entries.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Amir Goldstein <[email protected]>
Date: Tue, 24 Oct 2017 12:24:11 +0300
Subject: ovl: do not cleanup unsupported index entries

From: Amir Goldstein <[email protected]>

commit fa0096e3bad69ed6f34843fd7ae1c45ca987012a upstream.

With index=on, ovl_indexdir_cleanup() tries to cleanup invalid index entries (e.g. bad index name). This behavior could result in cleaning of entries created by newer kernels and is therefore undesirable. Instead, abort mount if such entries are encountered. We still cleanup 'stale' entries and 'orphan' entries, both those cases can be a result of offline changes to lower and upper dirs.

When encoutering an index entry of type directory or whiteout, kernel was supposed to fallback to read-only mount, but the fill_super() operation returns EROFS in this case instead of returning success with read-only mount flag, so mount fails when encoutering directory or whiteout index entries. Bless this behavior by returning -EINVAL on directory and whiteout index entries as we do for all unsupported index entries.

---
 fs/overlayfs/namei.c   |    7 +++----
 fs/overlayfs/readdir.c |   11 +++++------
 2 files changed, 8 insertions(+), 10 deletions(-)

@@ -405,14 +405,13 @@ int ovl_verify_index(struct dentry *inde
 	 * be treated as stale (i.e. after unlink of the overlay inode).
 	 * We don't know the verification rules for directory and whiteout
 	 * index entries, because they have not been implemented yet, so return
-	 * EROFS if those entries are found to avoid corrupting an index that
-	 * was created by a newer kernel.
+	 * EINVAL if those entries are found to abort the mount to avoid
+	 * corrupting an index that was created by a newer kernel.
 	 */
-	err = -EROFS;
+	err = -EINVAL;
 	if (d_is_dir(index) || ovl_is_whiteout(index))
 		goto fail;
 
-	err = -EINVAL;
 	if (index->d_name.len < sizeof(struct ovl_fh)*2)
 		goto fail;
 

@@ -704,13 +704,12 @@ int ovl_indexdir_cleanup(struct dentry *
 			break;
 		}
 		err = ovl_verify_index(index, lowerstack, numlower);
-		if (err) {
-			if (err == -EROFS)
-				break;
+		/* Cleanup stale and orphan index entries */
+		if (err && (err == -ESTALE || err == -ENOENT))
 			err = ovl_cleanup(dir, index);
-			if (err)
-				break;
-		}
+		if (err)
+			break;
+
 		dput(index);
 		index = NULL;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/ovl-handle-enoent-on-index-lookup.patch queue-4.13/ovl-fix-eio-from-lookup-of-non-indexed-upper.patch queue-4.13/ovl-do-not-cleanup-unsupported-index-entries.patch