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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B893C761AF for ; Tue, 4 Apr 2023 01:43:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231788AbjDDBnj (ORCPT ); Mon, 3 Apr 2023 21:43:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232406AbjDDBni (ORCPT ); Mon, 3 Apr 2023 21:43:38 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 929FDA2; Mon, 3 Apr 2023 18:43:37 -0700 (PDT) Received: from dggpemm500006.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Pr9Rq4XSGzSmM3; Tue, 4 Apr 2023 09:39:51 +0800 (CST) Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Tue, 4 Apr 2023 09:43:34 +0800 Subject: Re: [PATCH bpf-next] kallsyms: Disable preemption for find_kallsyms_symbol_value To: Jiri Olsa , Luis Chamberlain , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko CC: Artem Savkov , , , , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Petr Mladek , Viktor Malik References: <20230403220254.2191240-1-jolsa@kernel.org> From: "Leizhen (ThunderTown)" Message-ID: <0ae28022-42fb-b0fd-50e3-63a6d76c8c10@huawei.com> Date: Tue, 4 Apr 2023 09:43:34 +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: <20230403220254.2191240-1-jolsa@kernel.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 2023/4/4 6:02, Jiri Olsa wrote: > Artem reported suspicious RCU usage [1]. The reason is that verifier > calls find_kallsyms_symbol_value with preemption enabled which will > trigger suspicious RCU usage warning in rcu_dereference_sched call. > > Disabling preemption in find_kallsyms_symbol_value and adding > __find_kallsyms_symbol_value function. Reviewed-by: Zhen Lei > > Fixes: 31bf1dbccfb0 ("bpf: Fix attaching fentry/fexit/fmod_ret/lsm to modules") > [1] https://lore.kernel.org/bpf/ZBrPMkv8YVRiWwCR@samus.usersys.redhat.com/ > Reported-by: Artem Savkov > Signed-off-by: Jiri Olsa > --- > kernel/module/kallsyms.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c > index ab2376a1be88..bdc911dbcde5 100644 > --- a/kernel/module/kallsyms.c > +++ b/kernel/module/kallsyms.c > @@ -442,7 +442,7 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type, > } > > /* Given a module and name of symbol, find and return the symbol's value */ > -unsigned long find_kallsyms_symbol_value(struct module *mod, const char *name) > +static unsigned long __find_kallsyms_symbol_value(struct module *mod, const char *name) > { > unsigned int i; > struct mod_kallsyms *kallsyms = rcu_dereference_sched(mod->kallsyms); > @@ -466,7 +466,7 @@ static unsigned long __module_kallsyms_lookup_name(const char *name) > if (colon) { > mod = find_module_all(name, colon - name, false); > if (mod) > - return find_kallsyms_symbol_value(mod, colon + 1); > + return __find_kallsyms_symbol_value(mod, colon + 1); > return 0; > } > > @@ -475,7 +475,7 @@ static unsigned long __module_kallsyms_lookup_name(const char *name) > > if (mod->state == MODULE_STATE_UNFORMED) > continue; > - ret = find_kallsyms_symbol_value(mod, name); > + ret = __find_kallsyms_symbol_value(mod, name); > if (ret) > return ret; > } > @@ -494,6 +494,16 @@ unsigned long module_kallsyms_lookup_name(const char *name) > return ret; > } > > +unsigned long find_kallsyms_symbol_value(struct module *mod, const char *name) > +{ > + unsigned long ret; > + > + preempt_disable(); > + ret = __find_kallsyms_symbol_value(mod, name); > + preempt_enable(); > + return ret; > +} > + > int module_kallsyms_on_each_symbol(const char *modname, > int (*fn)(void *, const char *, > struct module *, unsigned long), > -- Regards, Zhen Lei