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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 92808C43603 for ; Thu, 5 Dec 2019 19:18:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6515624651 for ; Thu, 5 Dec 2019 19:18:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575573493; bh=IjLuAsJiaFdsPLJzv4fOjqC+NhLYxYJ5tvEVRrlmemc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=yTq6DEUAdzaaUzYvWUQHF+KYJk3v6zwSam7shbxziZux+3YWcJ43mtsM82HHSJN2f eg5jPnEAIZKbw7xuLnyPmTRnyS5IVgFPpslQZdorhN9PAixvjNJkOEFkf95KPoGRI5 8u0D07PCBy/fNJ/X3MSiKueYBFHEP1W7R/ThYX04= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729583AbfLETSM (ORCPT ); Thu, 5 Dec 2019 14:18:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:51712 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726028AbfLETSM (ORCPT ); Thu, 5 Dec 2019 14:18:12 -0500 Received: from linux-8ccs (ip-109-41-192-234.web.vodafone.de [109.41.192.234]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9AE5F2464D; Thu, 5 Dec 2019 19:18:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575573491; bh=IjLuAsJiaFdsPLJzv4fOjqC+NhLYxYJ5tvEVRrlmemc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mseQgxqXQDfkArNpXBPAAx7LPKXvi3zwrbbMwe1NVO+6OXgm329Qvsl2VvCaaN3Pz BbU8dWZOzR0hxGwzf8/pZ2XHIZLR0ouS7P1y/GSHAHdBE5ktvHyVuTrr77l6Grq02m XLGj5+I2M9ecsO/l3ce+emjg06ebpIvamEiWVbag= Date: Thu, 5 Dec 2019 20:17:59 +0100 From: Jessica Yu To: Masami Hiramatsu Cc: Joel Fernandes , Ingo Molnar , Anders Roxell , paulmck@kernel.org, "Naveen N . Rao" , Anil S Keshavamurthy , David Miller , Linux Kernel Mailing List Subject: Re: [PATCH] modules: lockdep: Suppress suspicious RCU usage warning Message-ID: <20191205191758.GA30613@linux-8ccs> References: <157535364480.17342.7937104819926015512.stgit@devnote2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <157535364480.17342.7937104819926015512.stgit@devnote2> X-OS: Linux linux-8ccs 4.12.14-lp150.12.61-default x86_64 User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Masami Hiramatsu [03/12/19 15:14 +0900]: >While running kprobe module test, find_module_all() caused >a suspicious RCU usage warning. > >----- > ============================= > WARNING: suspicious RCU usage > 5.4.0-next-20191202+ #63 Not tainted > ----------------------------- > kernel/module.c:619 RCU-list traversed in non-reader section!! > > other info that might help us debug this: > > > rcu_scheduler_active = 2, debug_locks = 1 > 1 lock held by rmmod/642: > #0: ffffffff8227da80 (module_mutex){+.+.}, at: __x64_sys_delete_module+0x9a/0x230 > > stack backtrace: > CPU: 0 PID: 642 Comm: rmmod Not tainted 5.4.0-next-20191202+ #63 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 > Call Trace: > dump_stack+0x71/0xa0 > find_module_all+0xc1/0xd0 > __x64_sys_delete_module+0xac/0x230 > ? do_syscall_64+0x12/0x1f0 > do_syscall_64+0x50/0x1f0 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x4b6d49 >----- > >This is because list_for_each_entry_rcu(modules) is called >without rcu_read_lock(). This is safe because the module_mutex >is locked. > >Pass lockdep_is_held(&module_lock) to the list_for_each_entry_rcu() s/module_lock/module_mutex/, but you don't have to respin the patch just for this. >to suppress this warning, This also fixes similar issue in >mod_find() and each_symbol_section(). > >Signed-off-by: Masami Hiramatsu Thanks Masami! This looks good. I'll queue this up shortly after the merge window. Jessica >--- > kernel/module.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > >diff --git a/kernel/module.c b/kernel/module.c >index cb6250be6ee9..38e5c6a7451b 100644 >--- a/kernel/module.c >+++ b/kernel/module.c >@@ -214,7 +214,8 @@ static struct module *mod_find(unsigned long addr) > { > struct module *mod; > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, >+ lockdep_is_held(&module_mutex)) { > if (within_module(addr, mod)) > return mod; > } >@@ -448,7 +449,8 @@ bool each_symbol_section(bool (*fn)(const struct symsearch *arr, > if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data)) > return true; > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, >+ lockdep_is_held(&module_mutex)) { > struct symsearch arr[] = { > { mod->syms, mod->syms + mod->num_syms, mod->crcs, > NOT_GPL_ONLY, false }, >@@ -616,7 +618,8 @@ static struct module *find_module_all(const char *name, size_t len, > > module_assert_mutex_or_preempt(); > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, >+ lockdep_is_held(&module_mutex)) { > if (!even_unformed && mod->state == MODULE_STATE_UNFORMED) > continue; > if (strlen(mod->name) == len && !memcmp(mod->name, name, len)) >