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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 C96B0C76186 for ; Wed, 17 Jul 2019 08:36:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7C3320818 for ; Wed, 17 Jul 2019 08:36:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726188AbfGQIgp (ORCPT ); Wed, 17 Jul 2019 04:36:45 -0400 Received: from a.mx.secunet.com ([62.96.220.36]:34262 "EHLO a.mx.secunet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725873AbfGQIgo (ORCPT ); Wed, 17 Jul 2019 04:36:44 -0400 Received: from localhost (localhost [127.0.0.1]) by a.mx.secunet.com (Postfix) with ESMTP id BEF62201E3; Wed, 17 Jul 2019 10:36:42 +0200 (CEST) X-Virus-Scanned: by secunet Received: from a.mx.secunet.com ([127.0.0.1]) by localhost (a.mx.secunet.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 5AFfrnKOEgbx; Wed, 17 Jul 2019 10:36:42 +0200 (CEST) Received: from mail-essen-01.secunet.de (mail-essen-01.secunet.de [10.53.40.204]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by a.mx.secunet.com (Postfix) with ESMTPS id 534432008D; Wed, 17 Jul 2019 10:36:42 +0200 (CEST) Received: from gauss2.secunet.de (10.182.7.193) by mail-essen-01.secunet.de (10.53.40.204) with Microsoft SMTP Server id 14.3.439.0; Wed, 17 Jul 2019 10:36:42 +0200 Received: by gauss2.secunet.de (Postfix, from userid 1000) id AB9F1318055E; Wed, 17 Jul 2019 10:36:41 +0200 (CEST) Date: Wed, 17 Jul 2019 10:36:41 +0200 From: Steffen Klassert To: Herbert Xu CC: Daniel Jordan , , , , , , , Subject: Re: [v2 PATCH] padata: Use RCU when fetching pd from do_serial Message-ID: <20190717083641.GQ17989@gauss3.secunet.de> References: <20190712100636.mqdr567p7ozanlyl@gondor.apana.org.au> <20190712101012.GW14601@gauss3.secunet.de> <20190712160737.iniaaxlsnhs6azg5@ca-dmjordan1.us.oracle.com> <20190713050321.c5wq7a7jrb6q2pxn@gondor.apana.org.au> <20190715161045.zqwgsp62uqjnvx3l@ca-dmjordan1.us.oracle.com> <20190716100447.pdongriwwfxsuajf@gondor.apana.org.au> <20190716111410.GN17989@gauss3.secunet.de> <20190716125704.l2jolyyd3bue6hhn@gondor.apana.org.au> <20190716130928.ga4acvxipsdzyzlp@gondor.apana.org.au> <20190716132345.ujj2v3kqra2lbi75@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20190716132345.ujj2v3kqra2lbi75@gondor.apana.org.au> User-Agent: Mutt/1.9.4 (2018-02-28) X-EXCLAIMER-MD-CONFIG: 2c86f778-e09b-4440-8b15-867914633a10 Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Tue, Jul 16, 2019 at 09:23:45PM +0800, Herbert Xu wrote: > On Tue, Jul 16, 2019 at 09:09:28PM +0800, Herbert Xu wrote: > > > > Hmm, it doesn't work because the refcnt is attached to the old > > pd. That shouldn't be a problem though as we could simply ignore > > the refcnt in padata_flush_queue. > > This should fix it: > > ---8<--- > The function padata_do_serial uses parallel_data without obeying > the RCU rules around its life-cycle. This means that a concurrent > padata_replace call can result in a crash. > > This patch fixes it by using RCU just as we do in padata_do_parallel. RCU alone won't help because if some object is queued for async crypto, we left the RCU protected aera. I think padata_do_serial needs to do RCU and should free 'parallel_data' if the flag PADATA_RESET is set and the refcount goes to zero. padata_replace should do the same then. > > As the refcnt may now span two parallel_data structures, this patch > moves it to padata_instance instead. FWIW the refcnt is used to > limit the number of outstanding requests (albeit a soft limit as > we don't do a proper atomic inc and test). > > Fixes: 16295bec6398 ("padata: Generic parallelization/...") > Signed-off-by: Herbert Xu > > diff --git a/include/linux/padata.h b/include/linux/padata.h ... > index 5d13d25da2c8..ce51555cb86c 100644 > @@ -367,7 +367,7 @@ void padata_do_serial(struct padata_priv *padata) > struct parallel_data *pd; > int reorder_via_wq = 0; > > - pd = padata->pd; > + pd = rcu_dereference_bh(padata->inst->pd); Why not just pd = rcu_dereference_bh(padata->pd);