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=-7.1 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 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 F3516C43603 for ; Fri, 6 Dec 2019 01:21:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C645420706 for ; Fri, 6 Dec 2019 01:21:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575595298; bh=K1h8wFONOn7HT/lNn+s3G3vdjhN2dKx00KjNLngfK+M=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=vPO2yov4PQUR8brsE35HZiiBUJGswpb4IUqLyypfPwjJwaYTcWZig5tezUF2+Lx8h 6H9A5+X+GjHC1irMjbTTof5njhegR5gStWWFfGs3KEkXLsao+cHDX/Pm+kp3B8kPwq xo0M8BWiCPhLQaVO53gKX80n0i5/Ve8WoGH9REo8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726222AbfLFBVh (ORCPT ); Thu, 5 Dec 2019 20:21:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:37638 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726047AbfLFBVh (ORCPT ); Thu, 5 Dec 2019 20:21:37 -0500 Received: from devnote2 (unknown [180.22.253.92]) (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 A83DB20706; Fri, 6 Dec 2019 01:21:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575595296; bh=K1h8wFONOn7HT/lNn+s3G3vdjhN2dKx00KjNLngfK+M=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=bPcRouQUCD3tUBN5DglqLZgQtFGem0bkK1X7+YvZb95D1ICcL5+fpPFhdOQ5y6/3f QIXeC81PsXwnVKOe9mzSIghwBNC2V3NpYkEKNGgxyefkiAXEeHYVA7KKVxXb5VttnN mpHT9NUuJEW9BpFJ5LW5hCX3+Uj94tDDL7x3owSs= Date: Fri, 6 Dec 2019 10:21:29 +0900 From: Masami Hiramatsu To: Jessica Yu 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: <20191206102129.abe60bfefb78048d4ab1d3cc@kernel.org> In-Reply-To: <20191205191758.GA30613@linux-8ccs> References: <157535364480.17342.7937104819926015512.stgit@devnote2> <20191205191758.GA30613@linux-8ccs> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 5 Dec 2019 20:17:59 +0100 Jessica Yu wrote: > +++ 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. Oops. > > >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. Thank you for merging :) > > 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)) > > -- Masami Hiramatsu