Merge tag 'ovl-fixes-5.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs fixes from Miklos Szeredi:
 "Fix some bugs and documentation"

* tag 'ovl-fixes-5.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  docs: filesystems: overlayfs: Fix restview warnings
  docs: filesystems: overlayfs: Rename overlayfs.txt to .rst
  ovl: relax WARN_ON() on rename to self
  ovl: fix corner case of non-unique st_dev;st_ino
  ovl: don't use a temp buf for encoding real fh
  ovl: make sure that real fid is 32bit aligned in memory
  ovl: fix lookup failure on multi lower squashfs

1 files changed, 17 insertions, 7 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index afbcb116a7f1..7621ff176d15 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1255,7 +1255,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
 {
 	unsigned int i;
 
-	if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt))
+	if (!ofs->config.nfs_export && !ofs->upper_mnt)
 		return true;
 
 	for (i = 0; i < ofs->numlowerfs; i++) {
@@ -1263,9 +1263,13 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
 		 * We use uuid to associate an overlay lower file handle with a
 		 * lower layer, so we can accept lower fs with null uuid as long
 		 * as all lower layers with null uuid are on the same fs.
+		 * if we detect multiple lower fs with the same uuid, we
+		 * disable lower file handle decoding on all of them.
 		 */
-		if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid))
+		if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) {
+			ofs->lower_fs[i].bad_uuid = true;
 			return false;
+		}
 	}
 	return true;
 }
@@ -1277,6 +1281,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
 	unsigned int i;
 	dev_t dev;
 	int err;
+	bool bad_uuid = false;
 
 	/* fsid 0 is reserved for upper fs even with non upper overlay */
 	if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
@@ -1288,11 +1293,15 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
 	}
 
 	if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
-		ofs->config.index = false;
-		ofs->config.nfs_export = false;
-		pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
-			uuid_is_null(&sb->s_uuid) ? "null" : "conflicting",
-			path->dentry);
+		bad_uuid = true;
+		if (ofs->config.index || ofs->config.nfs_export) {
+			ofs->config.index = false;
+			ofs->config.nfs_export = false;
+			pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
+				uuid_is_null(&sb->s_uuid) ? "null" :
+							    "conflicting",
+				path->dentry);
+		}
 	}
 
 	err = get_anon_bdev(&dev);
@@ -1303,6 +1312,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
 
 	ofs->lower_fs[ofs->numlowerfs].sb = sb;
 	ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
+	ofs->lower_fs[ofs->numlowerfs].bad_uuid = bad_uuid;
 	ofs->numlowerfs++;
 
 	return ofs->numlowerfs;