From patchwork Mon Feb 3 18:56:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qian Cai X-Patchwork-Id: 1232984 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=lca.pw header.i=@lca.pw header.a=rsa-sha256 header.s=google header.b=ZhvyRhZd; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48BHJT1tMbz9sRQ for ; Tue, 4 Feb 2020 06:02:33 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726366AbgBCTCT (ORCPT ); Mon, 3 Feb 2020 14:02:19 -0500 Received: from mail-qt1-f195.google.com ([209.85.160.195]:39126 "EHLO mail-qt1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727023AbgBCS4r (ORCPT ); Mon, 3 Feb 2020 13:56:47 -0500 Received: by mail-qt1-f195.google.com with SMTP id c5so12287673qtj.6 for ; Mon, 03 Feb 2020 10:56:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=from:to:cc:subject:date:message-id; bh=VwnXekGQXSa7uk8525c/XCF18A7jAwffbm1SfA/XcX4=; b=ZhvyRhZdwPSk7E9iCxSIx3EugvYG564eEnnAlJ/ouVluCpK2VPQykwpEsqeRNgUitR W/BuFusZ27zSDBT+/jYTFFymspJ3dERHirQZvBgZVrPNxvcQm66owTyXKCVV1yAM+Sxc Bc3MKo0HUrcNJ72m8XBBipQotrgt+vwcAEYdeU7BYEaU8lMCQPv6JYIiTQF4Soit1oRW lqzcMVDoNq4Du3f4O9oS0xAciHWKOnCi07fTyMVmG8psBJbz6t/3KtdULlIkacbymLvz b9KRuLJfKpSWd+C74YlFiOGFUD9mabLukExPKGdNs58NJOCldOOgwEQ5mRN7wA9RbOl/ ettg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=VwnXekGQXSa7uk8525c/XCF18A7jAwffbm1SfA/XcX4=; b=KsnUwytsvjvVXaRTnBh4Mpx3dAweEWo7GsCRlSkm8/RQAz1doPwOV60otOT5uRPqPe BM6/KraPHpP1hJQANO/4OysA8xrkFlrt8BAebmqD2tL6IrzHH7BnnfL1ryvrsiKwisNg H/BNp7D9Up3z1es3owwB6BgNRq5MfXprGch/4LhzDVhnAmsjvbdset49Bvhn6pndmz1N a1sE9kVpfMBobvbk06DuFkSxsgoDSfgYzMRYT8mnFZmmey1q7G8v3eDjNEu+FQBf5zHI OVtTbs0o5rvh5RUnV1DkyCDM0GED7W556JH4U9MVqeowfJXusHv8e9UGYnxXAggr65QA Hjhg== X-Gm-Message-State: APjAAAWOhuM5DWWLZkqSk76WxkRVNF8V/iEbpM81H41r9Ra4ovB78u1I fscoC7CC1282xdOtblKltUo8SQ== X-Google-Smtp-Source: APXvYqwPf1/ipGCfx3eQPpZLwPLV0xEziSVZYePbcGHclQRptnOnIRJbIK+DKn9LkhEgbFE/x02lNg== X-Received: by 2002:ac8:4b6f:: with SMTP id g15mr24999365qts.196.1580756205793; Mon, 03 Feb 2020 10:56:45 -0800 (PST) Received: from qcai.nay.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id v18sm9694220qkg.67.2020.02.03.10.56.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 03 Feb 2020 10:56:44 -0800 (PST) From: Qian Cai To: davem@davemloft.net Cc: kuba@kernel.org, elver@google.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH] skbuff: fix a data race in skb_queue_len() Date: Mon, 3 Feb 2020 13:56:30 -0500 Message-Id: <1580756190-3541-1-git-send-email-cai@lca.pw> X-Mailer: git-send-email 1.8.3.1 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org sk_buff.qlen can be accessed concurrently as noticed by KCSAN, BUG: KCSAN: data-race in __skb_try_recv_from_queue / unix_dgram_sendmsg read to 0xffff8a1b1d8a81c0 of 4 bytes by task 5371 on cpu 96: unix_dgram_sendmsg+0x9a9/0xb70 include/linux/skbuff.h:1821 net/unix/af_unix.c:1761 ____sys_sendmsg+0x33e/0x370 ___sys_sendmsg+0xa6/0xf0 __sys_sendmsg+0x69/0xf0 __x64_sys_sendmsg+0x51/0x70 do_syscall_64+0x91/0xb47 entry_SYSCALL_64_after_hwframe+0x49/0xbe write to 0xffff8a1b1d8a81c0 of 4 bytes by task 1 on cpu 99: __skb_try_recv_from_queue+0x327/0x410 include/linux/skbuff.h:2029 __skb_try_recv_datagram+0xbe/0x220 unix_dgram_recvmsg+0xee/0x850 ____sys_recvmsg+0x1fb/0x210 ___sys_recvmsg+0xa2/0xf0 __sys_recvmsg+0x66/0xf0 __x64_sys_recvmsg+0x51/0x70 do_syscall_64+0x91/0xb47 entry_SYSCALL_64_after_hwframe+0x49/0xbe Since only the read is operating as lockless, it could introduce a logic bug in unix_recvq_full() due to the load tearing. Fix it by adding a READ_ONCE() there. Signed-off-by: Qian Cai --- include/linux/skbuff.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 3d13a4b717e9..4b5157164f3e 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1818,7 +1818,7 @@ static inline struct sk_buff *skb_peek_tail(const struct sk_buff_head *list_) */ static inline __u32 skb_queue_len(const struct sk_buff_head *list_) { - return list_->qlen; + return READ_ONCE(list_->qlen); } /**