From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ursula Braun Subject: Re: [PATCH v2] net/smc: fix TCP fallback socket release Date: Mon, 17 Dec 2018 15:58:58 +0100 Message-ID: References: <20181217052122.GA26299@myunghoj-Precision-5530> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Myungho Jung Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:49182 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387546AbeLQO7F (ORCPT ); Mon, 17 Dec 2018 09:59:05 -0500 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wBHEwsMV126688 for ; Mon, 17 Dec 2018 09:59:04 -0500 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2pebneesd4-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 17 Dec 2018 09:59:04 -0500 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 17 Dec 2018 14:59:02 -0000 In-Reply-To: <20181217052122.GA26299@myunghoj-Precision-5530> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 12/17/2018 06:21 AM, Myungho Jung wrote: > clcsock can be released while kernel_accept() references it in TCP > listen worker. Also, clcsock needs to wake up before released if TCP > fallback is used and the clcsock is blocked by accept. Add a lock to > safely release clcsock and call kernel_sock_shutdown() to wake up > clcsock from accept in smc_release(). Thanks for your effort to solve this problem. I have some minor improvement proposals: > > Reported-by: syzbot+0bf2e01269f1274b4b03@syzkaller.appspotmail.com > Reported-by: syzbot+e3132895630f957306bc@syzkaller.appspotmail.com > Signed-off-by: Myungho Jung > --- > net/smc/af_smc.c | 14 ++++++++++++-- > net/smc/smc.h | 2 ++ > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c > index 5fbaf1901571..5d06fb1bbccf 100644 > --- a/net/smc/af_smc.c > +++ b/net/smc/af_smc.c > @@ -147,8 +147,14 @@ static int smc_release(struct socket *sock) > sk->sk_shutdown |= SHUTDOWN_MASK; > } > if (smc->clcsock) { > + if (smc->use_fallback && sk->sk_state == SMC_LISTEN) { > + /* wake up clcsock accept */ > + rc = kernel_sock_shutdown(smc->clcsock, SHUT_RDWR); > + } This part is not needed, since an SMC socket in state SMC_LISTEN is never a use_fallback socket. > + mutex_lock(&smc->clcsock_release_lock); > sock_release(smc->clcsock); > smc->clcsock = NULL; > + mutex_unlock(&smc->clcsock_release_lock); > } > if (smc->use_fallback) { > if (sk->sk_state != SMC_LISTEN && sk->sk_state != SMC_INIT) > @@ -205,6 +211,7 @@ static struct sock *smc_sock_alloc(struct net *net, struct socket *sock, > spin_lock_init(&smc->conn.send_lock); > sk->sk_prot->hash(sk); > sk_refcnt_debug_inc(sk); > + mutex_init(&smc->clcsock_release_lock); > > return sk; > } > @@ -821,7 +828,7 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc) > struct socket *new_clcsock = NULL; > struct sock *lsk = &lsmc->sk; > struct sock *new_sk; > - int rc; > + int rc = 0; Without clcsock the good path should not be executed. Thus I suggest to initialize with something negative like -EINVAL. > > release_sock(lsk); > new_sk = smc_sock_alloc(sock_net(lsk), NULL, lsk->sk_protocol); > @@ -834,7 +841,10 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc) > } > *new_smc = smc_sk(new_sk); > > - rc = kernel_accept(lsmc->clcsock, &new_clcsock, 0); > + mutex_lock(&lsmc->clcsock_release_lock); > + if (lsmc->clcsock) > + rc = kernel_accept(lsmc->clcsock, &new_clcsock, 0); > + mutex_unlock(&lsmc->clcsock_release_lock); > lock_sock(lsk); > if (rc < 0) > lsk->sk_err = -rc; > diff --git a/net/smc/smc.h b/net/smc/smc.h > index 08786ace6010..9a2795cf5d30 100644 > --- a/net/smc/smc.h > +++ b/net/smc/smc.h > @@ -219,6 +219,8 @@ struct smc_sock { /* smc sock container */ > * started, waiting for unsent > * data to be sent > */ > + struct mutex clcsock_release_lock; > + /* protects clcsock */ I suggest to be more precise: "protects clcsock of a listen socket" > }; > > static inline struct smc_sock *smc_sk(const struct sock *sk) >