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Tue, 02 Jul 2024 03:48:36 -0400 X-MC-Unique: N1PiBs12N7qL7xkUAQdo7A-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A6D4319560AA; Tue, 2 Jul 2024 07:48:34 +0000 (UTC) Received: from [10.39.208.23] (unknown [10.39.208.23]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CEC901956089; Tue, 2 Jul 2024 07:48:32 +0000 (UTC) Message-ID: <1c002c66-08a7-465c-bb56-a22abb7c840e@redhat.com> Date: Tue, 2 Jul 2024 09:48:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] vhost: fix crash caused by accessing a freed vsocket To: Gongming Chen , chenbox@nvidia.com Cc: dev@dpdk.org, Gongming Chen , stable@dpdk.org References: From: Maxime Coquelin Autocrypt: addr=maxime.coquelin@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi Gongming, On 5/10/24 09:28, Gongming Chen wrote: > Hi Maxime and Chenbo, > > Do you have any suggestions for how to address this? > > Looking forward to hearing from you! Could you please have a try with latest DPDK main branch, and if it reproduces, rebase your series on top of it. I don't think it has been fixed, but we've done significant changes in fdman in this release so we need a rebase anyways. Thanks in advance, Maxime > > Thanks, > Gongming > >> On Apr 3, 2024, at 11:52 PM, Gongming Chen wrote: >> >> Hi Maxime, >> Thanks for review. >> >>> On Apr 3, 2024, at 5:39 PM, Maxime Coquelin wrote: >>> >>> Hi Gongming, >>> >>> It's the 9th time the patch has been sent. >>> I'm not sure whether there are changes between them or these are just >>> re-sends, but that's something to avoid. >>> >> >> Sorry, there's something wrong with my mailbox. >> I will send a v1 version as the latest patch, but they are actually the same. >> >>> If there are differences, you should use versionning to highlight it. >>> If unsure, please check the contributions guidelines first. >>> >>> Regarding the patch itself, I don't know if this is avoidable, but I >>> would prefer we do not introduce yet another lock in there. >>> >>> Thanks, >>> Maxime >>> >> >> I totally agree with your. >> Therefore, initially I hoped to solve this problem without introducing >> new lock. However, the result was not expected. >> >> 1. The vsocket is shared between the event and reconnect threads by >> transmitting the vsocket pointer. Therefore, there is no way to protect >> vsocket through a simple vsocket lock. >> >> 2. The event and reconnect threads can transmit vsocket pointers to >> each other, so there is no way to ensure that vsocket will not be >> accessed by locking the two threads separately. >> >> 3. Therefore, on the vsocket resource, event and reconnect are in the >> same critical section. Only by locking two threads at the same time >> can the vsocket be ensured that it will not be accessed and can be >> freed safely. >> >> Currently, app config, event, and reconnect threads respectively have >> locks corresponding to their own maintenance resources, >> vhost_user.mutex, pfdset->fd_mutex, and reconn_list.mutex. >> >> I think there is a thread-level lock missing here to protect the >> critical section between threads, just like the rcu scene protection. >> >> After app config acquires the write lock, it ensures that the event and >> reconnect threads are outside the critical section. >> This is to completely clean up the resources associated with vsocket >> and safely free vsocket. >> >> Therefore, considering future expansion, if there may be more >> resources like vsocket, this thread lock can also be used to ensure >> that resources are safely released after complete cleanup. >> >> In this way, the threads will be clearer, and the complicated try lock >> method is no longer needed. >> >> Thanks, >> Gongming >