ovl: check namelen

We already calculate f_namelen in statfs as the maximum of the name lengths
provided by the filesystems taking part in the overlay.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/namei.c

@@ -20,7 +20,8 @@ static struct dentry *ovl_lookup_real(struct dentry *dir,
 
 	dentry = lookup_one_len_unlocked(name->name, dir, name->len);
 	if (IS_ERR(dentry)) {
-		if (PTR_ERR(dentry) == -ENOENT)
+		if (PTR_ERR(dentry) == -ENOENT ||
+		    PTR_ERR(dentry) == -ENAMETOOLONG)
 			dentry = NULL;
 	} else if (!dentry->d_inode) {
 		dput(dentry);
@@ -74,6 +75,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 {
 	struct ovl_entry *oe;
 	const struct cred *old_cred;
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
 	struct path *stack = NULL;
 	struct dentry *upperdir, *upperdentry = NULL;
@@ -86,6 +88,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	unsigned int i;
 	int err;
 
+	if (dentry->d_name.len > ofs->namelen)
+		return ERR_PTR(-ENAMETOOLONG);
+
 	old_cred = ovl_override_creds(dentry->d_sb);
 	upperdir = ovl_upperdentry_dereference(poe);
 	if (upperdir) {
@@ -127,14 +132,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 
 		this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
 		err = PTR_ERR(this);
-		if (IS_ERR(this)) {
-			/*
-			 * If it's positive, then treat ENAMETOOLONG as ENOENT.
-			 */
-			if (err == -ENAMETOOLONG && (upperdentry || ctr))
-				continue;
+		if (IS_ERR(this))
 			goto out_put;
-		}
+
 		if (!this)
 			continue;
 		if (ovl_is_whiteout(this)) {

fs/overlayfs/ovl_entry.h

@@ -21,7 +21,7 @@ struct ovl_fs {
 	unsigned numlower;
 	struct vfsmount **lower_mnt;
 	struct dentry *workdir;
-	long lower_namelen;
+	long namelen;
 	/* pathnames of lower and upper dirs, for show_options */
 	struct ovl_config config;
 	/* creds of process who forced instantiation of super block */

fs/overlayfs/super.c

@@ -174,7 +174,7 @@ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 
 	err = vfs_statfs(&path, buf);
 	if (!err) {
-		buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
+		buf->f_namelen = ofs->namelen;
 		buf->f_type = OVERLAYFS_SUPER_MAGIC;
 	}
 
@@ -461,22 +461,33 @@ static int ovl_mount_dir(const char *name, struct path *path)
 	return err;
 }
 
-static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
-			 int *stack_depth, bool *remote)
+static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
+			     const char *name)
 {
-	int err;
 	struct kstatfs statfs;
+	int err = vfs_statfs(path, &statfs);
+
+	if (err)
+		pr_err("overlayfs: statfs failed on '%s'\n", name);
+	else
+		ofs->namelen = max(ofs->namelen, statfs.f_namelen);
+
+	return err;
+}
+
+static int ovl_lower_dir(const char *name, struct path *path,
+			 struct ovl_fs *ofs, int *stack_depth, bool *remote)
+{
+	int err;
 
 	err = ovl_mount_dir_noesc(name, path);
 	if (err)
 		goto out;
 
-	err = vfs_statfs(path, &statfs);
-	if (err) {
-		pr_err("overlayfs: statfs failed on '%s'\n", name);
+	err = ovl_check_namelen(path, ofs, name);
+	if (err)
 		goto out_put;
-	}
-	*namelen = max(*namelen, statfs.f_namelen);
+
 	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
 
 	if (ovl_dentry_remote(path->dentry))
@@ -708,6 +719,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 			goto out_put_upperpath;
 		}
 
+		err = ovl_check_namelen(&upperpath, ufs, ufs->config.upperdir);
+		if (err)
+			goto out_put_upperpath;
+
 		err = ovl_mount_dir(ufs->config.workdir, &workpath);
 		if (err)
 			goto out_put_upperpath;
@@ -745,9 +760,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 
 	lower = lowertmp;
 	for (numlower = 0; numlower < stacklen; numlower++) {
-		err = ovl_lower_dir(lower, &stack[numlower],
-				    &ufs->lower_namelen, &sb->s_stack_depth,
-				    &remote);
+		err = ovl_lower_dir(lower, &stack[numlower], ufs,
+				    &sb->s_stack_depth, &remote);
 		if (err)
 			goto out_put_lowerpath;