From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E77D1476694; Thu, 10 Sep 2026 11:34:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789040087; cv=none; b=gIurG+gek8oEysW6dAeUZOu523Wc6g8WrcNhgBke2qsUF9eqhtcZIShkEMbDrYP9SniHajEbtgv61Gf5SmkTke1ILdv9GseGCpVjTw8FmThlJLia+heuHhcsth9F0xepRnfRk4qqvwkXXu2ZYGF+7jMVHyBXmWbNPFb35V3MGMM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789040087; c=relaxed/simple; bh=hDqWr9xlRvgArq+mx7X+y24g7DkLFSDkDAQjpM/Z4tg=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=jt8U0Zt3HPa6lbLolqWyvtkWxnBpwA3G+VsRhiI9mUxZQ6ud/JRmkfud3WJvo5PUCe01qbyIU9a1ONv0SxWU4705+7Z4dxwtwSQm8Zejabr6o6J3515kyM90nLeWtlZPOOkToUXaqHDjHtEYT3e12qRA2S1rg1Cnm4jaS1LHLr0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oGAxyzPh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oGAxyzPh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B5271F000FF; Thu, 10 Sep 2026 11:34:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789040085; bh=H0/yLvJdO0IIgjpyHZ96Avcg6Gv1RvJhM1p0WfML1Wc=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=oGAxyzPhpn/DIRDvf86kJnSmwK+su5Vdi2qqj06IMjW/BUyadxW4A+YZ70EpFLbSi v8s9nxYL5o/xf7l1Lp3pnJOULofRiLjx5QJQErSjthYdIfBITeSXfh0XyzAW4RPFdw 7q/jtNRRYJhFZzCP7iLTLBHAOEcv32gIqD9vdt9hQ1OIXHZNLrDEvfF08VTgxeFzBQ qt0E2pL0aWMv28WfKobxvBUfHJiBAGVpzm48jGC3y962G6zfmSd/IYm8rubw++n78s USQeAg6XOPloQwEwa2mXtmw0/hpT+3TJsvKvsQBbUumHMB3UWWvfvOiJhjL4mfZ181 /iToBXOl9l4RQ== Message-ID: <1df4f57669494c7684b140dba7c7226475ea68c9.camel@kernel.org> Subject: Re: [RFC PATCH 0/2] quota evasion test and nfs helpers From: Jeff Layton To: cem@kernel.org, zlang@kernel.org Cc: djwong@kernel.org, hch@lst.de, linux-xfs@vger.kernel.org, fstests@vger.kernel.org, jack@suse.cz, linux-nfs@vger.kernel.org, Chuck Lever Date: Thu, 10 Sep 2026 07:34:43 -0400 In-Reply-To: <20260907164054.111393-1-cem@kernel.org> References: <20260907164054.111393-1-cem@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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> Hi folks. >=20 > I'm flagging these as RFC because I'd like an input in the approach I > took here regarding how to setup a local nfs-server to reproduce the bug > recently fixed on xfs quotas. >=20 > The issue is regarding how we checked the credentials before proceeding > with quota enforcement / or not. And due the chgrp() being run through a > NSF share, xfs used the wrong credentials allowing an user to evade > quotas. >=20 > The TL;DR; for the approach is: > - setup a xfs fs with an user belonging to two groups with group > quotas enforced > - Setup a local nfs server/client and mount it locally through > loopback > - use the user to fill in the share until it exceeds quota > - change group of the file to the second group. > - repeat a couple times until the second group quota is > exceeded. >=20 > I'm using the already existing user/groups. The tests uses exportfs direc= tly > instead of seeting up a exports file, and I added a few new helpers to > start/stop nfsd and rpcbind. The latter I did as an attempt to make the t= est > systemd-agnostic. It is working even if nfs-server systemd service is dis= abled, > but I didn't try on a systemd-less OS. >=20 > While writing it I stumped on a weird issue that I'm not exactly sure > how to fix (or if it's perhaps a bug on umount): >=20 > During cleanup(), I umount the share and unexport the it so the rest > of the generic cleanup can take place, specially umounting the scratch > fs There is some timing though required by umount() to properly cleanup > internal kernel structures before it can be unexported. I honestly > assumed umount() was synchronous (unless lazy umount) and once it returne= d > it was "done". But for some reason I didn't dig into, I need to wait a > bit between unmounting the share and unexporting it. > I tried to wait until the mount was excluded from /proc/mounts but even > after the mount is gone, something still holds the share a bit > preventing it to be unexported. So I went with a 2 second sleep :) >=20 It may be that nfsd still has some state held here that is being cleaned up. Chuck has a patchset in progress that may help this: https://lore.kernel.org/linux-nfs/20260419-umount-kills-nfsv4-state-v9-0-06= 60bd06d2b6@oracle.com/ > Overall the test works, passing on a patched kernel or failing > otherwise. >=20 > Comments? Flames? Stones? >=20 > Cheers. >=20 > Carlos Maiolino (2): > common/nfs: add management helpers > generic: add test for quota enforcement via a nfs share >=20 > common/nfs | 55 ++++++++++++++++++++++ > tests/generic/803 | 106 ++++++++++++++++++++++++++++++++++++++++++ > tests/generic/803.out | 2 + > 3 files changed, 163 insertions(+) > create mode 100755 tests/generic/803 > create mode 100644 tests/generic/803.out --=20 Jeff Layton