[Bug 2025302] Re: mount.nfs: sloppy options processing is broken on 5.15 HWE kernel

[Matthew Ruffell]

Hi Heitor, it is a clean cherry pick. I always use "backport" in the
origin field. Maybe I should start using "upstream" for cherry picks
going forward and keep "backport" for things that actually needed
modifying.

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Title:
  mount.nfs: sloppy options processing is broken on 5.15 HWE kernel

Status in nfs-utils package in Ubuntu:
  Fix Released
Status in nfs-utils source package in Focal:
  In Progress

Bug description:
  [Impact]

  There was a new mount API introduced to the nfs subsystem in the 5.6
  kernel release, that changed how parameters should be passed from
  userspace mount.nfs to the kernel.

  This broke processing of the sloppy '-s' and '-o' options, where if
  you have an invalid mount option, or the ordering of mount options was
  incorrect, the mount would fail instead of going through.

  The fix is to move the sloppy options to the front of the options
  list, and then passing the rest of the options to the kernel, so the
  sloppy operator can be parsed correctly.

  [Testcase]

  Start two Focal VMs, one for the server, and one for the client.

  On the Server:
  1) sudo apt update
  2) sudo apt install nfs-kernel-server
  3) sudo mkdir -p /mnt/nfs_share
  4) sudo chown -R nobody:nogroup /mnt/nfs_share/
  5) sudo chmod 777 /mnt/nfs_share/
  6) echo "/mnt/nfs_share 192.168.122.0/24(rw,sync,no_subtree_check)" | sudo tee /etc/exports
  7) sudo exportfs -a
  8) sudo systemctl restart nfs-kernel-server
  9) echo "Testfile" | tee /mnt/nfs_share/testfile

  On the client:
  1) sudo apt update
  2) sudo apt install nfs-common
  3) sudo mkdir -p /mnt/nfs_clientshare
  4) sudo mount -t nfs 192.168.122.114:/mnt/nfs_share /mnt/nfs_clientshare -s -o invalid,intr

  On the client with 5.4 kernel:

  $ uname -rv
  5.4.0-152-generic #169-Ubuntu SMP Tue Jun 6 22:23:09 UTC 2023
  $ sudo mount -t nfs 192.168.122.114:/mnt/nfs_share /mnt/nfs_clientshare -s -o invalid,intr
  $ cd /mnt/nfs_clientshare/
  /mnt/nfs_clientshare$ ll
  total 12
  drwxrwxrwx 2 nobody nogroup 4096 Jun 29 01:13 ./
  drwxr-xr-x 3 root   root    4096 Jun 29 01:11 ../
  -rw-rw-r-- 1 ubuntu ubuntu     9 Jun 29 01:13 testfile
  /mnt/nfs_clientshare$ cat testfile 
  Testfile

  On the client with the 5.15 HWE kernel:

  $ uname -rv
  5.15.0-76-generic #83~20.04.1-Ubuntu SMP Wed Jun 21 20:23:31 UTC 2023
  $ sudo mount -t nfs 192.168.122.114:/mnt/nfs_share /mnt/nfs_clientshare -s -o invalid,intr
  mount.nfs: an incorrect mount option was specified

  There are test packages in the following ppa:

  https://launchpad.net/~mruffell/+archive/ubuntu/sf352441-test

  If you install them, when using the HWE kernel, you will see:

  $ uname -rv
  5.15.0-76-generic #83~20.04.1-Ubuntu SMP Wed Jun 21 20:23:31 UTC 2023
  $ sudo mount -t nfs 192.168.122.114:/mnt/nfs_share /mnt/nfs_clientshare -s -o invalid,intr
  $ cd /mnt/nfs_clientshare/
  /mnt/nfs_clientshare$ ll
  total 12
  drwxrwxrwx 2 nobody nogroup 4096 Jun 29 01:13 ./
  drwxr-xr-x 3 root   root    4096 Jun 29 01:11 ../
  -rw-rw-r-- 1 ubuntu ubuntu     9 Jun 29 01:13 testfile
  /mnt/nfs_clientshare$ cat testfile 
  Testfile

  [Where problems could occur]

  We are changing how options parameters are parsed. If a regression
  were to occur, user's nfs mount commands might fail, which has the
  possibility of breaking nfs-clients. If a system is set to mount a
  share on boot, a share might not be available without manual
  intervention.

  Users should not have to modify their mount commands at all. But if a
  regression were to occur, sysadmins may need to change to the ordering
  of their options.

  This does not change nfs-servers, only nfs-clients.

  [Other Info]

  This issue was fixed in 2.6.1 of nfs-utils with the following commits:

  commit 92b664ef4f25f1bd920bea4db435345629543353
  From: Jianhong Yin <yin-jianhong at 163.com>
  Date: Thu, 10 Jun 2021 13:27:29 -0400
  Subject: mount.nfs: insert 'sloppy' at beginning of the options
  Link: https://git.linux-nfs.org/?p=steved/nfs-utils.git;a=patch;h=92b664ef4f25f1bd920bea4db435345629543353

  commit 4dd8d833c9350d42528ada0fd65aee41b712f41d
  From: Steve Dickson <steved at redhat.com>
  Date: Tue, 20 Jul 2021 17:14:04 -0400
  Subject: mount.nfs: Fix the sloppy option processing
  Link: https://git.linux-nfs.org/?p=steved/nfs-utils.git;a=patch;h=4dd8d833c9350d42528ada0fd65aee41b712f41d

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