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=-13.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 A84CCC47426 for ; Tue, 29 Sep 2020 12:43:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A41B20725 for ; Tue, 29 Sep 2020 12:43:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601383432; bh=38R1XRDeld8qdJ08DT4Ym8pB1pC/aOYXW2X/W5I6pks=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=y7k9ikztwIzDtnOOq8RfBkFHfNFRzVtPieIk7Vsm/ApTrMk39BBNRzS0LJaNVCYEd LUXc0cgaoYxgy/I18S7NlJGbbkJ4HnOVdWghRgMQSLLX12jHJJuudLfSrZzBVtgkpz bUpGsxQn2nLtbexXTiT1gjyydXv0COZTjBEyjQXQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728722AbgI2LJq (ORCPT ); Tue, 29 Sep 2020 07:09:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:47416 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728264AbgI2LIf (ORCPT ); Tue, 29 Sep 2020 07:08:35 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 0C21721D43; Tue, 29 Sep 2020 11:08:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601377708; bh=38R1XRDeld8qdJ08DT4Ym8pB1pC/aOYXW2X/W5I6pks=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q6HEJPpv+FdlgsNdODcApBKct52aPktMN5RUSvduJqRovjaOTfeMOylfekxOlXHp1 GKk4pLxyILSm2SngJS9JCtzvDvyMt55MHX2g2g7L+CK366LAXFG791nDUO/w4gj2TB RzXk4oou+AsvpnEnbvbo7NR6C/8xzcXGjdC5ELZY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qian Cai , "David S. Miller" , Sasha Levin Subject: [PATCH 4.9 044/121] skbuff: fix a data race in skb_queue_len() Date: Tue, 29 Sep 2020 12:59:48 +0200 Message-Id: <20200929105932.372911098@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929105930.172747117@linuxfoundation.org> References: <20200929105930.172747117@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Qian Cai [ Upstream commit 86b18aaa2b5b5bb48e609cd591b3d2d0fdbe0442 ] 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 lockless variant of skb_queue_len() and unix_recvq_full() where READ_ONCE() is on the read while WRITE_ONCE() is on the write similar to the commit d7d16a89350a ("net: add skb_queue_empty_lockless()"). Signed-off-by: Qian Cai Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- include/linux/skbuff.h | 14 +++++++++++++- net/unix/af_unix.c | 11 +++++++++-- 2 files changed, 22 insertions(+), 3 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index fe4b7e4883431..67b798b7115d8 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1549,6 +1549,18 @@ static inline __u32 skb_queue_len(const struct sk_buff_head *list_) return list_->qlen; } +/** + * skb_queue_len_lockless - get queue length + * @list_: list to measure + * + * Return the length of an &sk_buff queue. + * This variant can be used in lockless contexts. + */ +static inline __u32 skb_queue_len_lockless(const struct sk_buff_head *list_) +{ + return READ_ONCE(list_->qlen); +} + /** * __skb_queue_head_init - initialize non-spinlock portions of sk_buff_head * @list: queue to initialize @@ -1752,7 +1764,7 @@ static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list) { struct sk_buff *next, *prev; - list->qlen--; + WRITE_ONCE(list->qlen, list->qlen - 1); next = skb->next; prev = skb->prev; skb->next = skb->prev = NULL; diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 32ae82a5596d9..bcd6ed6e7e25c 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -191,11 +191,17 @@ static inline int unix_may_send(struct sock *sk, struct sock *osk) return unix_peer(osk) == NULL || unix_our_peer(sk, osk); } -static inline int unix_recvq_full(struct sock const *sk) +static inline int unix_recvq_full(const struct sock *sk) { return skb_queue_len(&sk->sk_receive_queue) > sk->sk_max_ack_backlog; } +static inline int unix_recvq_full_lockless(const struct sock *sk) +{ + return skb_queue_len_lockless(&sk->sk_receive_queue) > + READ_ONCE(sk->sk_max_ack_backlog); +} + struct sock *unix_peer_get(struct sock *s) { struct sock *peer; @@ -1793,7 +1799,8 @@ restart_locked: * - unix_peer(sk) == sk by time of get but disconnected before lock */ if (other != sk && - unlikely(unix_peer(other) != sk && unix_recvq_full(other))) { + unlikely(unix_peer(other) != sk && + unix_recvq_full_lockless(other))) { if (timeo) { timeo = unix_wait_for_peer(other, timeo); -- 2.25.1