Ubuntu
zfs-linux package

zfs: can't read /proc/sys/kernel/spl/hostid

Bug #1942991 reported by Colin Ian King
8
This bug affects 1 person
Affects Status Importance Assigned to Milestone
zfs-linux (Ubuntu)
Fix Released
Medium
Colin Ian King
Hirsute
Fix Released
Medium
Colin Ian King
Impish
Fix Released
Medium
Colin Ian King

Bug Description

[Impact]

Reading /proc/sys/kernel/spl/hostid no longer works in 5.7+ kernels upwards.

The Fix:

commit 7de4c88b39473f358add601e8c227ca9002b1bee
Author: наб <email address hidden>
Date: Sun Apr 11 01:18:40 2021 +0200
linux/spl: base proc_dohostid() on proc_dostring()

    This fixes /proc/sys/kernel/spl/hostid on kernels with mainline commit
    32927393dc1ccd60fb2bdc05b9e8e88753761469 ("sysctl: pass kernel pointers
    to ->proc_handler") ‒ 5.7-rc1 and up

    The access_ok() check in copy_to_user() in proc_copyout_string() would
    always fail, so all userspace reads and writes would fail with EINVAL

    proc_dostring() strips only the final new-line,
    but simple_strtoul() doesn't actually need a back-trimmed string ‒
    writing "012345678 \n" is still allowed, as is "012345678zupsko", &c.

    This alters what happens when an invalid value is written ‒
    previously it'd get set to what-ever simple_strtoul() returned
    (probably 0, thereby resetting it to default), now it does nothing

    Reviewed-by: Brian Behlendorf <email address hidden>
    Signed-off-by: Ahelenia Ziemiańska <email address hidden>
    Closes #11878
    Closes #11879

This applies cleanly for Impish and Hirsute 2.x ZFS so backporting is straight forward.

[Test Plan]

cat /proc/sys/kernel/spl/hostid fails without the fix. With the fix it returns a hex string of the hostid value.

[Where problems could occur]

This affects just a few /proc spl interfaces so the change is a low-impact fix. Not many folk even use these and nobody has reported this as a bug so the number of affected users is expected to be very small. I suspect nobody is reading the hostid from /proc as this information is available elsewhere and it's rather an old legacy interface.

The affected change is from upstream ZFS 2.x hence the patch applies cleanly.

This fix has been in upstream ZFS for several months with no reported regressions.

The change does not affect any core ZFS functionality.

Regression tested against the Ubuntu ZFS regression test suite and passed.

See original description
Colin Ian King (colin-king)
Changed in zfs-linux (Ubuntu):
importance: Undecided → Medium
status: New → In Progress
assignee: nobody → Colin Ian King (colin-king)
Colin Ian King (colin-king)
Changed in zfs-linux (Ubuntu Hirsute):
assignee: nobody → Colin Ian King (colin-king)
status: New → In Progress
importance: Undecided → Medium
Colin Ian King (colin-king)
description: updated
Colin Ian King (colin-king)
description: updated
Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package zfs-linux - 2.0.3-8ubuntu8

---------------
zfs-linux (2.0.3-8ubuntu8) impish; urgency=medium

  * Fix /proc/sys/kernel/spl/hostid (LP: #1942991)
   - 4750-linux-spl-base-proc_dohostid-on-proc_dostring.patch
  * Fix build issues with latest tool updates:
   - 4751-suppress-regex_t.patch
  * Move 470* patches to debian/ubuntu

 -- Colin Ian King <email address hidden> Tue, 7 Sep 2021 19:08:23 +0100

Changed in zfs-linux (Ubuntu Impish):
status: In Progress → Fix Released
Revision history for this message
Brian Murray (brian-murray) wrote :

Given what you've said in the description about this being a legacy interface and the number of users affected being very small what is motivating the SRU? Given that zfs-linux binary packages are seeded and widely installed does it make sense to force everyone to update?

Revision history for this message
Colin Ian King (colin-king) wrote (last edit ):

The issue is that reading the interface provides a weird kernel looking error on an invalid address and the fact that the kernel is trapping this and shoving a kernel error message into a proc text file looks plain bad and can concern users who read these files.

Revision history for this message
Brian Murray (brian-murray) wrote : Please test proposed package

Hello Colin, or anyone else affected,

Accepted zfs-linux into hirsute-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/zfs-linux/2.0.2-1ubuntu5.2 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-hirsute to verification-done-hirsute. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-hirsute. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Changed in zfs-linux (Ubuntu Hirsute):
status: In Progress → Fix Committed
Revision history for this message
Colin Ian King (colin-king) wrote :

Tested on Hirsute with version 2.0.2-1ubuntu5.2:

$ cat /proc/sys/kernel/spl/hostid
22559a3d

All working and tested fine.

Colin Ian King (colin-king)
tags: added: verification-done verification-done-hirsute
Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package zfs-linux - 2.0.2-1ubuntu5.2

---------------
zfs-linux (2.0.2-1ubuntu5.2) hirsute; urgency=medium

  * Fix /proc/sys/kernel/spl/hostid (LP: #1942991)
   - 4750-linux-spl-base-proc_dohostid-on-proc_dostring.patch

 -- Colin Ian King <email address hidden> Tue, 7 Sep 2021 19:08:23 +0100

Changed in zfs-linux (Ubuntu Hirsute):
status: Fix Committed → Fix Released
Revision history for this message
Brian Murray (brian-murray) wrote : Update Released

The verification of the Stable Release Update for zfs-linux has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

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