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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 66D47C3276C for ; Thu, 2 Jan 2020 22:25:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D77521835 for ; Thu, 2 Jan 2020 22:25:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578003957; bh=b/KwFZ07DpEj6OWIHnQKcIq3IybnsxcbJgAuNQzc85w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=A2ahk3z1lFNiVON1ll9VrcetbA3n9wZYDHqiW1JPiDcb6wGw/lL6o+Lp5X0yer0Mm DbC0Qrj78uEc5IsL4PbaLWSuJDG8bVU+Lq9VZZMIJN+PRYMZHaJTe0HCmH0CKXsahy d6TnEPdU7QFBJbqZ8Bj9dWx4MQnAWV5SIZ7feP3k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729587AbgABWZ4 (ORCPT ); Thu, 2 Jan 2020 17:25:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:52122 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729334AbgABWZw (ORCPT ); Thu, 2 Jan 2020 17:25:52 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 367FB20863; Thu, 2 Jan 2020 22:25:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578003951; bh=b/KwFZ07DpEj6OWIHnQKcIq3IybnsxcbJgAuNQzc85w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PxXIMJaLJtmljSwFOfyBMxErelpLwQFdicJ/W4j1ZJHel37czvIRT8u33fKhMUcQL /NS3Wa4p9tm/+VFP+d0SEcUeREsPjCQ5TxxbhvkYP1bHgvC2O/kbfNoudMVMyhEHRg fVx6V4JfNOVVEpuT8dfJgF25GwJxEnV3GNTyHQBQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , syzbot , "David S. Miller" Subject: [PATCH 4.14 68/91] net: add a READ_ONCE() in skb_peek_tail() Date: Thu, 2 Jan 2020 23:07:50 +0100 Message-Id: <20200102220444.875000284@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200102220356.856162165@linuxfoundation.org> References: <20200102220356.856162165@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet commit f8cc62ca3e660ae3fdaee533b1d554297cd2ae82 upstream. skb_peek_tail() can be used without protection of a lock, as spotted by KCSAN [1] In order to avoid load-stearing, add a READ_ONCE() Note that the corresponding WRITE_ONCE() are already there. [1] BUG: KCSAN: data-race in sk_wait_data / skb_queue_tail read to 0xffff8880b36a4118 of 8 bytes by task 20426 on cpu 1: skb_peek_tail include/linux/skbuff.h:1784 [inline] sk_wait_data+0x15b/0x250 net/core/sock.c:2477 kcm_wait_data+0x112/0x1f0 net/kcm/kcmsock.c:1103 kcm_recvmsg+0xac/0x320 net/kcm/kcmsock.c:1130 sock_recvmsg_nosec net/socket.c:871 [inline] sock_recvmsg net/socket.c:889 [inline] sock_recvmsg+0x92/0xb0 net/socket.c:885 ___sys_recvmsg+0x1a0/0x3e0 net/socket.c:2480 do_recvmmsg+0x19a/0x5c0 net/socket.c:2601 __sys_recvmmsg+0x1ef/0x200 net/socket.c:2680 __do_sys_recvmmsg net/socket.c:2703 [inline] __se_sys_recvmmsg net/socket.c:2696 [inline] __x64_sys_recvmmsg+0x89/0xb0 net/socket.c:2696 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x44/0xa9 write to 0xffff8880b36a4118 of 8 bytes by task 451 on cpu 0: __skb_insert include/linux/skbuff.h:1852 [inline] __skb_queue_before include/linux/skbuff.h:1958 [inline] __skb_queue_tail include/linux/skbuff.h:1991 [inline] skb_queue_tail+0x7e/0xc0 net/core/skbuff.c:3145 kcm_queue_rcv_skb+0x202/0x310 net/kcm/kcmsock.c:206 kcm_rcv_strparser+0x74/0x4b0 net/kcm/kcmsock.c:370 __strp_recv+0x348/0xf50 net/strparser/strparser.c:309 strp_recv+0x84/0xa0 net/strparser/strparser.c:343 tcp_read_sock+0x174/0x5c0 net/ipv4/tcp.c:1639 strp_read_sock+0xd4/0x140 net/strparser/strparser.c:366 do_strp_work net/strparser/strparser.c:414 [inline] strp_work+0x9a/0xe0 net/strparser/strparser.c:423 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269 worker_thread+0xa0/0x800 kernel/workqueue.c:2415 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 451 Comm: kworker/u4:3 Not tainted 5.4.0-rc3+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: kstrp strp_work Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/linux/skbuff.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1655,7 +1655,7 @@ static inline struct sk_buff *skb_peek_n */ static inline struct sk_buff *skb_peek_tail(const struct sk_buff_head *list_) { - struct sk_buff *skb = list_->prev; + struct sk_buff *skb = READ_ONCE(list_->prev); if (skb == (struct sk_buff *)list_) skb = NULL; @@ -1723,7 +1723,9 @@ static inline void __skb_insert(struct s struct sk_buff *prev, struct sk_buff *next, struct sk_buff_head *list) { - /* see skb_queue_empty_lockless() for the opposite READ_ONCE() */ + /* See skb_queue_empty_lockless() and skb_peek_tail() + * for the opposite READ_ONCE() + */ WRITE_ONCE(newsk->next, next); WRITE_ONCE(newsk->prev, prev); WRITE_ONCE(next->prev, newsk);