From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f196.google.com ([209.85.128.196]:35152 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935107AbeE2Ol5 (ORCPT ); Tue, 29 May 2018 10:41:57 -0400 Received: by mail-wr0-f196.google.com with SMTP id i14-v6so25957657wre.2 for ; Tue, 29 May 2018 07:41:56 -0700 (PDT) From: Miklos Szeredi To: linux-unionfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 07/11] ovl: make ovl_create_real() cope with vfs_mkdir() safely Date: Tue, 29 May 2018 16:41:39 +0200 Message-Id: <20180529144143.16378-8-mszeredi@redhat.com> In-Reply-To: <20180529144143.16378-1-mszeredi@redhat.com> References: <20180529144143.16378-1-mszeredi@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: From: Amir Goldstein vfs_mkdir() may succeed and leave the dentry passed to it unhashed and negative. ovl_create_real() is the last caller breaking when that happens. [amir: split re-factoring of ovl_create_temp() to prep patch add comment about unhashed dir after mkdir add pr_warn() if mkdir succeeds and lookup fails] Signed-off-by: Al Viro Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi --- fs/overlayfs/dir.c | 35 +++++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index 1b181292a624..b33d37d1a87c 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -114,6 +114,37 @@ int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir, goto out; } +static struct dentry *ovl_mkdir_real(struct inode *dir, struct dentry *dentry, + umode_t mode) +{ + int err; + + err = ovl_do_mkdir(dir, dentry, mode); + if (err) { + dput(dentry); + return ERR_PTR(err); + } + + /* + * vfs_mkdir() may succeed and leave the dentry passed + * to it unhashed and negative. If that happens, try to + * lookup a new hashed and positive dentry. + */ + if (unlikely(d_unhashed(dentry))) { + struct dentry *d; + + d = lookup_one_len(dentry->d_name.name, dentry->d_parent, + dentry->d_name.len); + if (IS_ERR(d)) { + pr_warn("overlayfs: failed lookup after mkdir (%pd2, err=%i).\n", + dentry, err); + } + dput(dentry); + dentry = d; + } + return dentry; +} + struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry, struct ovl_cattr *attr) { @@ -135,8 +166,8 @@ struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry, break; case S_IFDIR: - err = ovl_do_mkdir(dir, newdentry, attr->mode); - break; + /* mkdir is special... */ + return ovl_mkdir_real(dir, newdentry, attr->mode); case S_IFCHR: case S_IFBLK: -- 2.14.3