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Mon, 23 May 2022 12:45:24 +0000 (GMT) Received: from [9.152.222.246] (unknown [9.152.222.246]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 23 May 2022 12:45:24 +0000 (GMT) Message-ID: <5ce801b7-d446-ee28-86ec-968b7c172a80@linux.ibm.com> Date: Mon, 23 May 2022 14:45:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH v2 net] net/smc: postpone sk_refcnt increment in connect() Content-Language: en-US To: liuyacan@corp.netease.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ubraun@linux.ibm.com References: <20220523032437.1059718-1-liuyacan@corp.netease.com> <20220523045707.1704761-1-liuyacan@corp.netease.com> From: Karsten Graul Organization: IBM Deutschland Research & Development GmbH In-Reply-To: <20220523045707.1704761-1-liuyacan@corp.netease.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: XS6ue79_VJDWrIuVKCYHMQQeybYcJo7C X-Proofpoint-ORIG-GUID: AYMnS93NXUhsfJM5lTDPzqC0LYAC7BbE X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-23_06,2022-05-23_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 suspectscore=0 mlxlogscore=999 priorityscore=1501 bulkscore=0 impostorscore=0 mlxscore=0 malwarescore=0 spamscore=0 adultscore=0 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205230069 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/05/2022 06:57, liuyacan@corp.netease.com wrote: > From: liuyacan > > Same trigger condition as commit 86434744. When setsockopt runs > in parallel to a connect(), and switch the socket into fallback > mode. Then the sk_refcnt is incremented in smc_connect(), but > its state stay in SMC_INIT (NOT SMC_ACTIVE). This cause the > corresponding sk_refcnt decrement in __smc_release() will not be > performed. > > Fixes: 86434744fedf ("net/smc: add fallback check to connect()") > Signed-off-by: liuyacan > --- > net/smc/af_smc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c > index fce16b9d6..45a24d242 100644 > --- a/net/smc/af_smc.c > +++ b/net/smc/af_smc.c > @@ -1564,9 +1564,9 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr, > if (rc && rc != -EINPROGRESS) > goto out; > > - sock_hold(&smc->sk); /* sock put in passive closing */ > if (smc->use_fallback) > goto out; > + sock_hold(&smc->sk); /* sock put in passive closing */ > if (flags & O_NONBLOCK) { > if (queue_work(smc_hs_wq, &smc->connect_work)) > smc->connect_nonblock = 1; This is a rather unusual problem that can come up when fallback=true BEFORE smc_connect() is called. But nevertheless, it is a problem. Right now I am not sure if it is okay when we NOT hold a ref to smc->sk during all fallback processing. This change also conflicts with a patch that is already on net-next (3aba1030). With the new patch on net-next it would also be possible to detect in __smc_release() that the socket is in state sk->sk_state == SMC_INIT but the sock->state is SS_CONNECTING or SS_CONNECTED and call sock_put() in this case. What do you think?