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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 DD3CDC636CA for ; Fri, 16 Jul 2021 05:03:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B99FA6109E for ; Fri, 16 Jul 2021 05:03:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233990AbhGPFGX (ORCPT ); Fri, 16 Jul 2021 01:06:23 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:11324 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229775AbhGPFGW (ORCPT ); Fri, 16 Jul 2021 01:06:22 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.57]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4GQzXs6yJcz7tbH; Fri, 16 Jul 2021 12:58:53 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 16 Jul 2021 13:03:24 +0800 Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Fri, 16 Jul 2021 13:03:23 +0800 Subject: Re: [PATCH] once: Fix panic when module unload To: , CC: Hannes Frederic Sowa , Daniel Borkmann , "David S . Miller" , "Eric Dumazet" , Minmin chen References: <20210622022138.23048-1-wangkefeng.wang@huawei.com> From: Kefeng Wang Message-ID: Date: Fri, 16 Jul 2021 13:03:23 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20210622022138.23048-1-wangkefeng.wang@huawei.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, kindly ping... On 2021/6/22 10:21, Kefeng Wang wrote: > DO_ONCE > DEFINE_STATIC_KEY_TRUE(___once_key); > __do_once_done > once_disable_jump(once_key); > INIT_WORK(&w->work, once_deferred); > struct once_work *w; > w->key = key; > schedule_work(&w->work); module unload > //*the key is destroy* > process_one_work > once_deferred > BUG_ON(!static_key_enabled(work->key)); > static_key_count((struct static_key *)x) //*access key, crash* > > When module uses DO_ONCE mechanism, it could crash due to the above > concurrency problem, we could reproduce it with link[1]. > > Fix it by add/put module refcount in the once work process. > > [1] > https://lore.kernel.org/netdev/eaa6c371-465e-57eb-6be9-f4b16b9d7cbf@huawei.com/ > > Cc: Hannes Frederic Sowa > Cc: Daniel Borkmann > Cc: David S. Miller > Cc: Eric Dumazet > Reported-by: Minmin chen > Signed-off-by: Kefeng Wang > --- > lib/once.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/lib/once.c b/lib/once.c > index 8b7d6235217e..959f8db41ccf 100644 > --- a/lib/once.c > +++ b/lib/once.c > @@ -3,10 +3,12 @@ > #include > #include > #include > +#include > > struct once_work { > struct work_struct work; > struct static_key_true *key; > + struct module *module; > }; > > static void once_deferred(struct work_struct *w) > @@ -16,11 +18,24 @@ static void once_deferred(struct work_struct *w) > work = container_of(w, struct once_work, work); > BUG_ON(!static_key_enabled(work->key)); > static_branch_disable(work->key); > + module_put(work->module); > kfree(work); > } > > +static struct module *find_module_by_key(struct static_key_true *key) > +{ > + struct module *mod; > + > + preempt_disable(); > + mod = __module_address((unsigned long)key); > + preempt_enable(); > + > + return mod; > +} > + > static void once_disable_jump(struct static_key_true *key) > { > + struct module *mod = find_module_by_key(key); > struct once_work *w; > > w = kmalloc(sizeof(*w), GFP_ATOMIC); > @@ -29,6 +44,8 @@ static void once_disable_jump(struct static_key_true *key) > > INIT_WORK(&w->work, once_deferred); > w->key = key; > + w->module = mod; > + __module_get(mod); > schedule_work(&w->work); > } >