From patchwork Thu Mar 17 03:08:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Iwashima, Kuniyuki" X-Patchwork-Id: 12783424 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 768ECC433FE for ; Thu, 17 Mar 2022 03:08:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243106AbiCQDKJ (ORCPT ); Wed, 16 Mar 2022 23:10:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35424 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236823AbiCQDKG (ORCPT ); Wed, 16 Mar 2022 23:10:06 -0400 Received: from smtp-fw-33001.amazon.com (smtp-fw-33001.amazon.com [207.171.190.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8185B21248 for ; Wed, 16 Mar 2022 20:08:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.co.jp; i=@amazon.co.jp; q=dns/txt; s=amazon201209; t=1647486531; x=1679022531; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=i9kHH3N2YgDgJx4J4nZNq8O3J1myq6j/lLoTD9s0gIw=; b=BuMA3sYR6Rmbvc7nPHeN/KAvxNljPHXhL5F0w7ikSUBoDFcVQ0JVtKkC +1z8SdXdJfwFoJN97LfgnxyZdOy6a1Svb/E+o94rVPwTM029H6m/sQNk0 bFacYvlS71U1oMD1oxpCoc05eU7gjq45YVOMyld8rMHx/J/R164CW03l6 Q=; X-IronPort-AV: E=Sophos;i="5.90,188,1643673600"; d="scan'208";a="182524605" Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO email-inbound-relay-iad-1a-b27d4a00.us-east-1.amazon.com) ([10.43.8.2]) by smtp-border-fw-33001.sea14.amazon.com with ESMTP; 17 Mar 2022 03:08:49 +0000 Received: from EX13MTAUWB001.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan3.iad.amazon.com [10.40.163.38]) by email-inbound-relay-iad-1a-b27d4a00.us-east-1.amazon.com (Postfix) with ESMTPS id C33DE814E1; Thu, 17 Mar 2022 03:08:47 +0000 (UTC) Received: from EX13D04ANC001.ant.amazon.com (10.43.157.89) by EX13MTAUWB001.ant.amazon.com (10.43.161.249) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Thu, 17 Mar 2022 03:08:46 +0000 Received: from 88665a182662.ant.amazon.com (10.43.160.100) by EX13D04ANC001.ant.amazon.com (10.43.157.89) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Thu, 17 Mar 2022 03:08:43 +0000 From: Kuniyuki Iwashima To: "David S. Miller" , Jakub Kicinski , Eric Dumazet , Rao Shoaib CC: Kuniyuki Iwashima , Kuniyuki Iwashima , Subject: [PATCH v4 net 1/2] af_unix: Fix some data-races around unix_sk(sk)->oob_skb. Date: Thu, 17 Mar 2022 12:08:08 +0900 Message-ID: <20220317030809.63672-2-kuniyu@amazon.co.jp> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220317030809.63672-1-kuniyu@amazon.co.jp> References: <20220317030809.63672-1-kuniyu@amazon.co.jp> MIME-Version: 1.0 X-Originating-IP: [10.43.160.100] X-ClientProxiedBy: EX13D04UWB004.ant.amazon.com (10.43.161.103) To EX13D04ANC001.ant.amazon.com (10.43.157.89) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Out-of-band data automatically places a "mark" showing wherein the sequence the out-of-band data would have been. If the out-of-band data implies cancelling everything sent so far, the "mark" is helpful to flush them. When the socket's read pointer reaches the "mark", the ioctl() below sets a non zero value to the arg `atmark`: The out-of-band data is queued in sk->sk_receive_queue as well as ordinary data and also saved in unix_sk(sk)->oob_skb. It can be used to test if the head of the receive queue is the out-of-band data meaning the socket is at the "mark". While testing that, unix_ioctl() reads unix_sk(sk)->oob_skb locklessly. Thus, all accesses to oob_skb need some basic protection to avoid load/store tearing which KCSAN detects when these are called concurrently: - ioctl(fd_a, SIOCATMARK, &atmark, sizeof(atmark)) - send(fd_b_connected_to_a, buf, sizeof(buf), MSG_OOB) BUG: KCSAN: data-race in unix_ioctl / unix_stream_sendmsg write to 0xffff888003d9cff0 of 8 bytes by task 175 on cpu 1: unix_stream_sendmsg (net/unix/af_unix.c:2087 net/unix/af_unix.c:2191) sock_sendmsg (net/socket.c:705 net/socket.c:725) __sys_sendto (net/socket.c:2040) __x64_sys_sendto (net/socket.c:2048) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:113) read to 0xffff888003d9cff0 of 8 bytes by task 176 on cpu 0: unix_ioctl (net/unix/af_unix.c:3101 (discriminator 1)) sock_do_ioctl (net/socket.c:1128) sock_ioctl (net/socket.c:1242) __x64_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:874 fs/ioctl.c:860 fs/ioctl.c:860) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:113) value changed: 0xffff888003da0c00 -> 0xffff888003da0d00 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 176 Comm: unix_race_oob_i Not tainted 5.17.0-rc5-59529-g83dc4c2af682 #12 Hardware name: Red Hat KVM, BIOS 1.11.0-2.amzn2 04/01/2014 Fixes: 314001f0bf92 ("af_unix: Add OOB support") Signed-off-by: Kuniyuki Iwashima --- net/unix/af_unix.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index c19569819866..0c37e5595aae 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2084,7 +2084,7 @@ static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other if (ousk->oob_skb) consume_skb(ousk->oob_skb); - ousk->oob_skb = skb; + WRITE_ONCE(ousk->oob_skb, skb); scm_stat_add(other, skb); skb_queue_tail(&other->sk_receive_queue, skb); @@ -2602,9 +2602,8 @@ static int unix_stream_recv_urg(struct unix_stream_read_state *state) oob_skb = u->oob_skb; - if (!(state->flags & MSG_PEEK)) { - u->oob_skb = NULL; - } + if (!(state->flags & MSG_PEEK)) + WRITE_ONCE(u->oob_skb, NULL); unix_state_unlock(sk); @@ -2639,7 +2638,7 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk, skb = NULL; } else if (sock_flag(sk, SOCK_URGINLINE)) { if (!(flags & MSG_PEEK)) { - u->oob_skb = NULL; + WRITE_ONCE(u->oob_skb, NULL); consume_skb(skb); } } else if (!(flags & MSG_PEEK)) { @@ -3094,11 +3093,10 @@ static int unix_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) case SIOCATMARK: { struct sk_buff *skb; - struct unix_sock *u = unix_sk(sk); int answ = 0; skb = skb_peek(&sk->sk_receive_queue); - if (skb && skb == u->oob_skb) + if (skb && skb == READ_ONCE(unix_sk(sk)->oob_skb)) answ = 1; err = put_user(answ, (int __user *)arg); }