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 CBA66C47255 for ; Mon, 11 May 2020 13:16:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC71220736 for ; Mon, 11 May 2020 13:16:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726173AbgEKNQi (ORCPT ); Mon, 11 May 2020 09:16:38 -0400 Received: from fieldses.org ([173.255.197.46]:54424 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726013AbgEKNQh (ORCPT ); Mon, 11 May 2020 09:16:37 -0400 Received: by fieldses.org (Postfix, from userid 2815) id 695401CB4; Mon, 11 May 2020 09:16:37 -0400 (EDT) Date: Mon, 11 May 2020 09:16:37 -0400 From: "J. Bruce Fields" To: Masayoshi Mizuma Cc: Trond Myklebust , Anna Schumaker , linux-nfs@vger.kernel.org Subject: Re: [PATCH] nfs: fix NULL deference in nfs4_get_valid_delegation Message-ID: <20200511131637.GA8629@fieldses.org> References: <20200508221935.GA11225@fieldses.org> <20200511121054.l2j34vnwqxhvd2ao@gabell> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200511121054.l2j34vnwqxhvd2ao@gabell> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org Thanks, applying.--b. On Mon, May 11, 2020 at 08:10:54AM -0400, Masayoshi Mizuma wrote: > On Fri, May 08, 2020 at 06:19:35PM -0400, J. Bruce Fields wrote: > > From: "J. Bruce Fields" > > > > We add the new state to the nfsi->open_states list, making it > > potentially visible to other threads, before we've finished initializing > > it. > > > > That wasn't a problem when all the readers were also taking the i_lock > > (as we do here), but since we switched to RCU, there's now a possibility > > that a reader could see the partially initialized state. > > > > Symptoms observed were a crash when another thread called > > nfs4_get_valid_delegation() on a NULL inode. > > > > Fixes: 9ae075fdd190 "NFSv4: Convert open state lookup to use RCU" > > Signed-off-by: J. Bruce Fields > > --- > > fs/nfs/nfs4state.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c > > index ac93715c05a4..a8dc25ce48bb 100644 > > --- a/fs/nfs/nfs4state.c > > +++ b/fs/nfs/nfs4state.c > > @@ -734,9 +734,9 @@ nfs4_get_open_state(struct inode *inode, struct nfs4_state_owner *owner) > > state = new; > > state->owner = owner; > > atomic_inc(&owner->so_count); > > - list_add_rcu(&state->inode_states, &nfsi->open_states); > > ihold(inode); > > state->inode = inode; > > + list_add_rcu(&state->inode_states, &nfsi->open_states); > > spin_unlock(&inode->i_lock); > > /* Note: The reclaim code dictates that we add stateless > > * and read-only stateids to the end of the list */ > > -- > > Thank you for posting the patch! It works for our box. > Please feel free to add: > > Reviewed-by: Seiichi Ikarashi > Tested-by: Daisuke Matsuda > Tested-by: Masayoshi Mizuma > > Without the patch, the system which is a NFSv4 client has been > crashed randomly. The panic log is such as: > > BUG: unable to handle page fault for address: ffffffffffffffb0 > ... > RIP: 0010:nfs4_get_valid_delegation+0x6/0x30 [nfsv4] > ... > Call Trace: > nfs4_open_prepare+0x80/0x1c0 [nfsv4] > __rpc_execute+0x75/0x390 [sunrpc] > ? finish_task_switch+0x75/0x260 > rpc_async_schedule+0x29/0x40 [sunrpc] > process_one_work+0x1ad/0x370 > worker_thread+0x30/0x390 > ? create_worker+0x1a0/0x1a0 > kthread+0x10c/0x130 > ? kthread_park+0x80/0x80 > ret_from_fork+0x22/0x30 > > After applied the patch, the panic is gone. > > Thanks! > Masa