Merge tag 'ovl-fixes-5.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs into master

Pull overlayfs fixes from Miklos Szeredi:

- fix a regression introduced in v4.20 in handling a regenerated
squashfs lower layer

- two regression fixes for this cycle, one of which is Oops inducing

- miscellaneous issues

* tag 'ovl-fixes-5.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: fix lookup of indexed hardlinks with metacopy
ovl: fix unneeded call to ovl_change_flags()
ovl: fix mount option checks for nfs_export with no upperdir
ovl: force read-only sb on failure to create index dir
ovl: fix regression with re-formatted lower squashfs
ovl: fix oops in ovl_indexdir_cleanup() with nfs_export=on
ovl: relax WARN_ON() when decoding lower directory file handle
ovl: remove not used argument in ovl_check_origin
ovl: change ovl_copy_up_flags static
ovl: inode reference leak in ovl_is_inuse true case.

Documentation/filesystems/overlayfs.rst

···
 verified on mount time to check that upper file handles are not stale.
 This verification may cause significant overhead in some cases.
 
-Note: the mount options index=off,nfs_export=on are conflicting and will
-result in an error.
+Note: the mount options index=off,nfs_export=on are conflicting for a
+read-write mount and will result in an error.
 
 
 Testsuite

fs/overlayfs/copy_up.c

···
 	return err;
 }
 
-int ovl_copy_up_flags(struct dentry *dentry, int flags)
+static int ovl_copy_up_flags(struct dentry *dentry, int flags)
 {
 	int err = 0;
 	const struct cred *old_cred = ovl_override_creds(dentry->d_sb);

fs/overlayfs/export.c

···
 	if (IS_ERR_OR_NULL(this))
 		return this;
 
-	if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) {
+	if (ovl_dentry_real_at(this, layer->idx) != real) {
 		dput(this);
 		this = ERR_PTR(-EIO);
 	}

fs/overlayfs/file.c

···
 		return 'm';
 }
 
+/* No atime modificaton nor notify on underlying */
+#define OVL_OPEN_FLAGS (O_NOATIME | FMODE_NONOTIFY)
+
 static struct file *ovl_open_realfile(const struct file *file,
 				      struct inode *realinode)
 {
 	struct inode *inode = file_inode(file);
 	struct file *realfile;
 	const struct cred *old_cred;
-	int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;
+	int flags = file->f_flags | OVL_OPEN_FLAGS;
 	int acc_mode = ACC_MODE(flags);
 	int err;
 
···
 	struct inode *inode = file_inode(file);
 	int err;
 
-	/* No atime modificaton on underlying */
-	flags |= O_NOATIME | FMODE_NONOTIFY;
+	flags |= OVL_OPEN_FLAGS;
 
 	/* If some flag changed that cannot be changed then something's amiss */
 	if (WARN_ON((file->f_flags ^ flags) & ~OVL_SETFL_MASK))
···
 	}
 
 	/* Did the flags change since open? */
-	if (unlikely((file->f_flags ^ real->file->f_flags) & ~O_NOATIME))
+	if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
 		return ovl_change_flags(real->file, file->f_flags);
 
 	return 0;

fs/overlayfs/namei.c

···
 }
 
 static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
-			    struct ovl_path **stackp, unsigned int *ctrp)
+			    struct ovl_path **stackp)
 {
 	struct ovl_fh *fh = ovl_get_fh(upperdentry, OVL_XATTR_ORIGIN);
 	int err;
···
 		return err;
 	}
 
-	if (WARN_ON(*ctrp))
-		return -EIO;
-
-	*ctrp = 1;
 	return 0;
 }
 
···
 			goto out;
 		}
 		if (upperdentry && !d.is_dir) {
-			unsigned int origin_ctr = 0;
-
 			/*
 			 * Lookup copy up origin by decoding origin file handle.
 			 * We may get a disconnected dentry, which is fine,
···
 			 * number - it's the same as if we held a reference
 			 * to a dentry in lower layer that was moved under us.
 			 */
-			err = ovl_check_origin(ofs, upperdentry, &origin_path,
-					       &origin_ctr);
+			err = ovl_check_origin(ofs, upperdentry, &origin_path);
 			if (err)
 				goto out_put_upper;
 
···
 			upperredirect = NULL;
 			goto out_free_oe;
 		}
+		err = ovl_check_metacopy_xattr(upperdentry);
+		if (err < 0)
+			goto out_free_oe;
+		uppermetacopy = err;
 	}
 
 	if (upperdentry || ctr) {

fs/overlayfs/overlayfs.h

···
 /* copy_up.c */
 int ovl_copy_up(struct dentry *dentry);
 int ovl_copy_up_with_data(struct dentry *dentry);
-int ovl_copy_up_flags(struct dentry *dentry, int flags);
 int ovl_maybe_copy_up(struct dentry *dentry, int flags);
 int ovl_copy_xattr(struct dentry *old, struct dentry *new);
 int ovl_set_attr(struct dentry *upper, struct kstat *stat);

fs/overlayfs/super.c

···
 		}
 	}
 
-	/* Workdir is useless in non-upper mount */
-	if (!config->upperdir && config->workdir) {
-		pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
-			config->workdir);
-		kfree(config->workdir);
-		config->workdir = NULL;
+	/* Workdir/index are useless in non-upper mount */
+	if (!config->upperdir) {
+		if (config->workdir) {
+			pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
+				config->workdir);
+			kfree(config->workdir);
+			config->workdir = NULL;
+		}
+		if (config->index && index_opt) {
+			pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
+			index_opt = false;
+		}
+		config->index = false;
 	}
 
 	err = ovl_parse_redirect_mode(config, config->redirect_mode);
···
 
 	/* Resolve nfs_export -> index dependency */
 	if (config->nfs_export && !config->index) {
-		if (nfs_export_opt && index_opt) {
+		if (!config->upperdir && config->redirect_follow) {
+			pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
+			config->nfs_export = false;
+		} else if (nfs_export_opt && index_opt) {
 			pr_err("conflicting options: nfs_export=on,index=off\n");
 			return -EINVAL;
-		}
-		if (index_opt) {
+		} else if (index_opt) {
 			/*
 			 * There was an explicit index=off that resulted
 			 * in this conflict.
···
 		goto out;
 	}
 
+	/* index dir will act also as workdir */
+	iput(ofs->workdir_trap);
+	ofs->workdir_trap = NULL;
+	dput(ofs->workdir);
+	ofs->workdir = NULL;
 	ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
 	if (ofs->indexdir) {
+		ofs->workdir = dget(ofs->indexdir);
+
 		err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
 				     "indexdir");
 		if (err)
···
 
 	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++) {
 		/*
···
 		if (err < 0)
 			goto out;
 
+		/*
+		 * Check if lower root conflicts with this overlay layers before
+		 * checking if it is in-use as upperdir/workdir of "another"
+		 * mount, because we do not bother to check in ovl_is_inuse() if
+		 * the upperdir/workdir is in fact in-use by our
+		 * upperdir/workdir.
+		 */
 		err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
 		if (err)
 			goto out;
 
 		if (ovl_is_inuse(stack[i].dentry)) {
 			err = ovl_report_in_use(ofs, "lowerdir");
-			if (err)
+			if (err) {
+				iput(trap);
 				goto out;
+			}
 		}
 
 		mnt = clone_private_mount(&stack[i]);
···
 	if (!ofs->config.upperdir && numlower == 1) {
 		pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
 		return ERR_PTR(-EINVAL);
-	} else if (!ofs->config.upperdir && ofs->config.nfs_export &&
-		   ofs->config.redirect_follow) {
-		pr_warn("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
-		ofs->config.nfs_export = false;
 	}
 
 	stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
···
 	if (!ovl_upper_mnt(ofs))
 		sb->s_flags |= SB_RDONLY;
 
-	if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
-		/* index dir will act also as workdir */
-		dput(ofs->workdir);
-		ofs->workdir = NULL;
-		iput(ofs->workdir_trap);
-		ofs->workdir_trap = NULL;
-
+	if (!ovl_force_readonly(ofs) && ofs->config.index) {
 		err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
 		if (err)
 			goto out_free_oe;
 
 		/* Force r/o mount with no index dir */
-		if (ofs->indexdir)
-			ofs->workdir = dget(ofs->indexdir);
-		else
+		if (!ofs->indexdir)
 			sb->s_flags |= SB_RDONLY;
 	}