From patchwork Mon Feb 22 19:12:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 386064 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AF02C433E9 for ; Mon, 22 Feb 2021 19:17:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 216E064F42 for ; Mon, 22 Feb 2021 19:17:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232858AbhBVTQ5 (ORCPT ); Mon, 22 Feb 2021 14:16:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232983AbhBVTNG (ORCPT ); Mon, 22 Feb 2021 14:13:06 -0500 Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [IPv6:2607:5300:60:148a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8376CC061794; Mon, 22 Feb 2021 11:12:26 -0800 (PST) Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94 #2 (Red Hat Linux)) id 1lEGd4-00HAzt-HJ; Mon, 22 Feb 2021 19:12:22 +0000 From: Al Viro To: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Christoph Hellwig , Jakub Kicinski , Denis Kirjanov , linux-fsdevel , Cong Wang Subject: [PATCH 6/8] unix_bind_bsd(): move done_path_create() call after dealing with ->bindlock Date: Mon, 22 Feb 2021 19:12:20 +0000 Message-Id: <20210222191222.4093800-6-viro@zeniv.linux.org.uk> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210222191222.4093800-1-viro@zeniv.linux.org.uk> References: <20210222191222.4093800-1-viro@zeniv.linux.org.uk> MIME-Version: 1.0 Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Final preparations for doing unlink on failure past the successful mknod. We can't hold ->bindlock over ->mknod() or ->unlink(), since either might do sb_start_write() (e.g. on overlayfs). However, we can do it while holding filesystem and VFS locks - doing kern_path_create() vfs_mknod() grab ->bindlock if u->addr had been set drop ->bindlock done_path_create return -EINVAL else assign the address to socket drop ->bindlock done_path_create return 0 would be deadlock-free. Here we massage unix_bind_bsd() to that form. We are still doing equivalent transformations. Next commit will *not* be an equivalent transformation - it will add a call of vfs_unlink() before done_path_create() in "alread bound" case. Signed-off-by: Al Viro --- net/unix/af_unix.c | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 5e04e16e6b88..368376621111 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -988,7 +988,7 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr) struct unix_sock *u = unix_sk(sk); umode_t mode = S_IFSOCK | (SOCK_INODE(sk->sk_socket)->i_mode & ~current_umask()); - struct path parent, path; + struct path parent; struct dentry *dentry; unsigned int hash; int err; @@ -1005,36 +1005,32 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr) * All right, let's create it. */ err = security_path_mknod(&parent, dentry, mode, 0); - if (!err) { + if (!err) err = vfs_mknod(d_inode(parent.dentry), dentry, mode, 0); - if (!err) { - path.mnt = mntget(parent.mnt); - path.dentry = dget(dentry); - } - } - done_path_create(&parent, dentry); - if (err) + if (err) { + done_path_create(&parent, dentry); return err; - + } err = mutex_lock_interruptible(&u->bindlock); if (err) { - path_put(&path); + done_path_create(&parent, dentry); return err; } - if (u->addr) { mutex_unlock(&u->bindlock); - path_put(&path); + done_path_create(&parent, dentry); return -EINVAL; } addr->hash = UNIX_HASH_SIZE; - hash = d_backing_inode(path.dentry)->i_ino & (UNIX_HASH_SIZE - 1); + hash = d_backing_inode(dentry)->i_ino & (UNIX_HASH_SIZE - 1); spin_lock(&unix_table_lock); - u->path = path; + u->path.mnt = mntget(parent.mnt); + u->path.dentry = dget(dentry); __unix_set_addr(sk, addr, hash); spin_unlock(&unix_table_lock); mutex_unlock(&u->bindlock); + done_path_create(&parent, dentry); return 0; }