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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 64A1FC04EBA for ; Wed, 28 Nov 2018 01:19:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D7D920851 for ; Wed, 28 Nov 2018 01:19:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2D7D920851 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=fieldses.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727195AbeK1MTJ (ORCPT ); Wed, 28 Nov 2018 07:19:09 -0500 Received: from fieldses.org ([173.255.197.46]:43818 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726539AbeK1MTJ (ORCPT ); Wed, 28 Nov 2018 07:19:09 -0500 Received: by fieldses.org (Postfix, from userid 2815) id 3FF4A1E68; Tue, 27 Nov 2018 20:19:23 -0500 (EST) Date: Tue, 27 Nov 2018 20:19:23 -0500 From: "J. Bruce Fields" To: Anatoly Trosinenko Cc: Jeff Layton , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: NFSd: NULL-dereference when writing to v4_end_grace when server is not yet started Message-ID: <20181128011923.GB15237@fieldses.org> References: <20181127205849.GB12810@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181127205849.GB12810@fieldses.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 27, 2018 at 03:58:49PM -0500, J. Bruce Fields wrote: > On Sun, Nov 25, 2018 at 09:17:10AM +0300, Anatoly Trosinenko wrote: > > When manually exploring the kernel NFSd feature, I have stumbled upon > > a NULL-dereference when writing to v4_end_grace when server is not yet > > started. > > Thanks for the report! > > I think this is what we want--it's what a lot of the other nfsctl > methods do. Hm, no, I'm getting a hang. It looks like in the nfsd4 state startup we call a cltrack upcall while holding the nfsd_mutex, then nfsdcltrack tries to write to end_grace. That's kind of ugly. --b. > commit ad5fdf47b4e3 > Author: J. Bruce Fields > Date: Tue Nov 27 15:54:17 2018 -0500 > > nfsd4: fix crash on writing v4_end_grace before nfsd startup > > Anatoly Trosinenko reports that this: > > 1) Checkout fresh master Linux branch (tested with commit e195ca6cb) > 2) Copy x84_64-config-4.14 to .config, then enable NFS server v4 and build > 3) From `kvm-xfstests shell`: > > results in NULL dereference in locks_end_grace. > > Check that nfsd has been started before trying to end the grace period. > > Reported-by: Anatoly Trosinenko > Signed-off-by: J. Bruce Fields > > diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c > index 6384c9b94898..38b223c1378e 100644 > --- a/fs/nfsd/nfsctl.c > +++ b/fs/nfsd/nfsctl.c > @@ -1126,7 +1126,13 @@ static ssize_t write_v4_end_grace(struct file *file, char *buf, size_t size) > case 'Y': > case 'y': > case '1': > + mutex_lock(&nfsd_mutex); > + if (nn->nfsd_serv) { > + mutex_unlock(&nfsd_mutex); > + return -EBUSY; > + } > nfsd4_end_grace(nn); > + mutex_unlock(&nfsd_mutex); > break; > default: > return -EINVAL;