From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ipmail06.adl2.internode.on.net ([150.101.137.129]:60762 "EHLO ipmail06.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751045AbeEBV7I (ORCPT ); Wed, 2 May 2018 17:59:08 -0400 Date: Thu, 3 May 2018 07:59:06 +1000 From: Dave Chinner Subject: Re: [PATCH] xfsprogs: be careful about what we stat in platform_check_mount Message-ID: <20180502215906.GD23861@dastard> References: <92bcf603-5106-9fa0-1b48-0d13ff0608c8@sandeen.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <92bcf603-5106-9fa0-1b48-0d13ff0608c8@sandeen.net> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Eric Sandeen Cc: linux-xfs On Wed, May 02, 2018 at 02:56:22PM -0500, Eric Sandeen wrote: > After we lost ustat(2) in commit 4e7a824, we ended up with a slightly > bonkers method to determine if our target block device was mounted: > it goes through every entry returned by getmntent and stats the dir > to see if its underlying device matches ours. > > Unfortunately that dir might be a hung nfs server and sadness ensues. > > So do some pre-checks; can we stat the mounted "device?" If so is > it really a block device? If not, skip it. > > Fixes: 4e7a824 ("libxfs/linux.c: Replace use of ustat by stat") > Signed-off-by: Eric Sandeen > --- > > diff --git a/libxfs/linux.c b/libxfs/linux.c > index 0bace3e..7350fa7 100644 > --- a/libxfs/linux.c > +++ b/libxfs/linux.c > @@ -77,7 +77,21 @@ platform_check_mount(char *name, char *block, struct stat *s, int flags) > progname, name); > return 1; > } > + /* > + * This whole business is to work out if our block device is mounted > + * after we lost ustat(2), see: > + * 4e7a824 libxfs/linux.c: Replace use of ustat by stat > + * We don't really want to stat every single mounted directory, > + * as that may include tmpfs, cgroups, procfs or - worst - hung nfs > + * servers. So we check the "device" before going after the mountpoint. > + */ > while ((mnt = getmntent(f)) != NULL) { > + /* If the "fsname" is't a stat-able device, skip it */ > + if (stat(mnt->mnt_fsname, &mst) < 0) > + continue; > + if (!S_ISBLK(mst.st_mode)) > + continue; That'll break with subvolumes - we'll be mounting regular files, not block devices.... Cheers, Dave. -- Dave Chinner david@fromorbit.com