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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 105BCC4338F for ; Fri, 23 Jul 2021 04:36:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D843860E93 for ; Fri, 23 Jul 2021 04:36:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233701AbhGWDzb (ORCPT ); Thu, 22 Jul 2021 23:55:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231760AbhGWDza (ORCPT ); Thu, 22 Jul 2021 23:55:30 -0400 Received: from ustc.edu.cn (email6.ustc.edu.cn [IPv6:2001:da8:d800::8]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0E91BC061575 for ; Thu, 22 Jul 2021 21:36:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mail.ustc.edu.cn; s=dkim; h=Received:Date:From:To:Cc:Subject: Message-ID:In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=QbTlxn9eNvcRhBOBCVeh2QYtVCInFts4u5 beNPEGQnc=; b=sSQhnsyJNfC/M5v9gQ3iNxU8w4XFxBPNG/B6MIhFsCy8GeEqg/ axSK/20lfKoUy+sZSpXqQtXSQBTB7PLSqa0yOwG7/ui0ibtbN37/z8BHHQjyTw4w zKfzOxpG48gsxjcNgQ+ivdua9TYvTikU9d2tGdbjgkEZ+l6mgkBbyNH3U= Received: from xhacker (unknown [101.86.20.15]) by newmailweb.ustc.edu.cn (Coremail) with SMTP id LkAmygB3fm4KR_pg5NUxAA--.1434S2; Fri, 23 Jul 2021 12:35:23 +0800 (CST) Date: Fri, 23 Jul 2021 12:29:25 +0800 From: Jisheng Zhang To: tongtiangen Cc: Andreas Schwab , Atish Patra , Palmer Dabbelt , Paul Walmsley , Albert Ou , linux-riscv , "linux-kernel@vger.kernel.org List" Subject: Re: [PATCH -next v2] riscv: add VMAP_STACK overflow detection Message-ID: <20210723122925.67a14562@xhacker> In-Reply-To: <52e3626a-2b40-bda6-de0e-68ea12a86dd9@huawei.com> References: <87bl6yrcmd.fsf@igel.home> <20210722213724.1f12a0e7@xhacker> <87zguexslf.fsf@igel.home> <20210723075432.098634a2@xhacker> <52e3626a-2b40-bda6-de0e-68ea12a86dd9@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: LkAmygB3fm4KR_pg5NUxAA--.1434S2 X-Coremail-Antispam: 1UD129KBjvJXoW7tw45Jr1UCry5XF18tr1kKrg_yoW8Wr18pF WUGay3tF4qva4xK3Z2qw18Wa409an7Ja45u3s5Xr13ZFZYg3Z5Xr4IgrWUKFW7Ww1IkayY vr4FqFZ7Wrs8Ja7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUyIb7Iv0xC_Cr1lb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwV C2z280aVCY1x0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC 0VAKzVAqx4xG6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr 1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y48IcVAKI48JMxAIw28IcxkI7VAKI48JMxC20s02 6xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_Jr I_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v2 6r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj4 0_WFyUJVCq3wCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j 6r4UJbIYCTnIWIevJa73UjIFyTuYvjxU7GYLDUUUU X-CM-SenderInfo: xmv2xttqjtqzxdloh3xvwfhvlgxou0/ Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 23 Jul 2021 09:36:47 +0800 tongtiangen wrote: > On 2021/7/23 7:54, Jisheng Zhang wrote: > > On Thu, 22 Jul 2021 17:42:52 +0200 > > Andreas Schwab wrote: > > =20 > >> On Jul 22 2021, Jisheng Zhang wrote: > >> =20 > >>> I think we need to pin the stack before calling get_wchan(), could yo= u please > >>> try below patch? =20 > >> > >> Thanks, this fixes the crash for me. > >> > >> Andreas. > >> =20 > > > > Thanks for testing. I will send out formal patch later > > > > Thanks > > > > . > > =20 >=20 > Hi all: > I tried to reproduced this crash in openSUSE code repo=EF=BC=88=20 > https://github.com/opensuse/kernel =EF=BC=89, but not reproduced successf= ully. >=20 > From the patch of problem repair, the crash is due to task->stack is=20 > released before calling get_wchan, the task state of maybe TASK_DEAD. >=20 > VMAP_STACK is used to detect kernel stack overflow, there is no=20 > connection between the two, it makes me a little confused. I believe the bug exists from the first day of riscv mainlined. Since THREAD_INFO_IN_TASK=3Dy in riscv, so when task stack can be freed before being destroyed. When VMAP_STACK=3Dn, task's stack is allocated from linear mapping. When task stack is freed, the corresponding mapping still exists, and since get_wchan() only read, no harm is observed so far. When VMAP_STACK=3Dy, task's stack is allocated from vmalloc area. When task stack is freed, the corresponding mapping may not exist, so I expect MMU fault here, thus the kernel panic. In summary, the bug isn't related with VMAP_STACK, but VMAP_STACK makes the bug observable. Thanks