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-rw-r--r--fs/overlayfs/super.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 31ef24dfcf88..94ca095b2a9e 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1402,6 +1402,18 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
return true;
+ /*
+ * We allow using single lower with null uuid for index and nfs_export
+ * for example to support those features with single lower squashfs.
+ * To avoid regressions in setups of overlay with re-formatted lower
+ * squashfs, do not allow decoding origin with lower null uuid unless
+ * user opted-in to one of the new features that require following the
+ * lower inode of non-dir upper.
+ */
+ if (!ofs->config.index && !ofs->config.metacopy && !ofs->config.xino &&
+ uuid_is_null(uuid))
+ return false;
+
for (i = 0; i < ofs->numfs; i++) {
/*
* We use uuid to associate an overlay lower file handle with a