Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751941AbdF3Hex (ORCPT ); Fri, 30 Jun 2017 03:34:53 -0400 Received: from mx2.suse.de ([195.135.220.15]:55625 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751784AbdF3Hew (ORCPT ); Fri, 30 Jun 2017 03:34:52 -0400 Date: Fri, 30 Jun 2017 09:34:48 +0200 From: Michal Kubecek To: netdev@vger.kernel.org Cc: WANG Cong , Rainer Weikusat , linux-kernel@vger.kernel.org Subject: RFC: changed error code when binding unix socket twice Message-ID: <20170630073448.GA9546@unicorn.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2327 Lines: 64 Hello, commit 0fb44559ffd6 ("af_unix: move unix_mknod() out of bindlock") moves the special file creation in unix_bind() before u->bindlock is taken in order to avoid an ABBA deadlock with do_splice(). As a side effect, it also moves the check for existence of the special file (which would result in -EADDRINUSE) before the check of u->addr (which would result in -EINVAL if socket is already bound). This means that the error returned for an attempt to bind a unix socket to the same path twice changed from -EINVAL to -EADDRINUSE with this commit. One way to restore the old error code is indicated below but before submitting it, I would like to ask if we need/want it. Pro: - in general, we do not want to change return code for given testcase - old error (-EINVAL) is consistent with AF_INET(6) Con: - both POSIX and Linux man page only list error conditions without stating which should take precedence if more of them apply so neither of them seems wrong, strictly speaking diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 1a0c961f4ffe..509292bdf7ed 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -992,7 +992,7 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) struct unix_sock *u = unix_sk(sk); struct sockaddr_un *sunaddr = (struct sockaddr_un *)uaddr; char *sun_path = sunaddr->sun_path; - int err; + int err, mknod_err; unsigned int hash; struct unix_address *addr; struct hlist_head *list; @@ -1016,12 +1016,10 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) if (sun_path[0]) { umode_t mode = S_IFSOCK | (SOCK_INODE(sock)->i_mode & ~current_umask()); - err = unix_mknod(sun_path, mode, &path); - if (err) { - if (err == -EEXIST) - err = -EADDRINUSE; - goto out; - } + mknod_err = unix_mknod(sun_path, mode, &path); + /* do not exit on error until after u->addr check */ + if (mknod_err == -EEXIST) + mknod_err = -EADDRINUSE; } err = mutex_lock_interruptible(&u->bindlock); @@ -1031,6 +1029,10 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) err = -EINVAL; if (u->addr) goto out_up; + if (mknod_err) { + err = mknod_err; + goto out_up; + } err = -ENOMEM; addr = kmalloc(sizeof(*addr)+addr_len, GFP_KERNEL);