From mboxrd@z Thu Jan 1 00:00:00 1970 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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 7B4DEC43142 for ; Sun, 24 Jun 2018 15:26:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F8F624F80 for ; Sun, 24 Jun 2018 15:26:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3F8F624F80 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752731AbeFXP0x (ORCPT ); Sun, 24 Jun 2018 11:26:53 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58746 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751849AbeFXP0v (ORCPT ); Sun, 24 Jun 2018 11:26:51 -0400 Received: from localhost (li1825-44.members.linode.com [172.104.248.44]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id DA94092F; Sun, 24 Jun 2018 15:26:49 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, shankarapailoor , Tetsuo Handa , Lorenzo Colitti , Al Viro , Cong Wang , "David S. Miller" Subject: [PATCH 4.14 07/52] socket: close race condition between sock_close() and sockfs_setattr() Date: Sun, 24 Jun 2018 23:21:00 +0800 Message-Id: <20180624142744.749974395@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180624142744.234164867@linuxfoundation.org> References: <20180624142744.234164867@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Cong Wang [ Upstream commit 6d8c50dcb029872b298eea68cc6209c866fd3e14 ] fchownat() doesn't even hold refcnt of fd until it figures out fd is really needed (otherwise is ignored) and releases it after it resolves the path. This means sock_close() could race with sockfs_setattr(), which leads to a NULL pointer dereference since typically we set sock->sk to NULL in ->release(). As pointed out by Al, this is unique to sockfs. So we can fix this in socket layer by acquiring inode_lock in sock_close() and checking against NULL in sockfs_setattr(). sock_release() is called in many places, only the sock_close() path matters here. And fortunately, this should not affect normal sock_close() as it is only called when the last fd refcnt is gone. It only affects sock_close() with a parallel sockfs_setattr() in progress, which is not common. Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.") Reported-by: shankarapailoor Cc: Tetsuo Handa Cc: Lorenzo Colitti Cc: Al Viro Signed-off-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/socket.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) --- a/net/socket.c +++ b/net/socket.c @@ -538,7 +538,10 @@ static int sockfs_setattr(struct dentry if (!err && (iattr->ia_valid & ATTR_UID)) { struct socket *sock = SOCKET_I(d_inode(dentry)); - sock->sk->sk_uid = iattr->ia_uid; + if (sock->sk) + sock->sk->sk_uid = iattr->ia_uid; + else + err = -ENOENT; } return err; @@ -588,12 +591,16 @@ EXPORT_SYMBOL(sock_alloc); * an inode not a file. */ -void sock_release(struct socket *sock) +static void __sock_release(struct socket *sock, struct inode *inode) { if (sock->ops) { struct module *owner = sock->ops->owner; + if (inode) + inode_lock(inode); sock->ops->release(sock); + if (inode) + inode_unlock(inode); sock->ops = NULL; module_put(owner); } @@ -608,6 +615,11 @@ void sock_release(struct socket *sock) } sock->file = NULL; } + +void sock_release(struct socket *sock) +{ + __sock_release(sock, NULL); +} EXPORT_SYMBOL(sock_release); void __sock_tx_timestamp(__u16 tsflags, __u8 *tx_flags) @@ -1122,7 +1134,7 @@ static int sock_mmap(struct file *file, static int sock_close(struct inode *inode, struct file *filp) { - sock_release(SOCKET_I(inode)); + __sock_release(SOCKET_I(inode), inode); return 0; }