Remove obsolete "nousb" option in kdump command-line for newer kernels

Bug #1800562 reported by Guilherme G. Piccoli on 2018-10-29
14
This bug affects 2 people
Affects Status Importance Assigned to Milestone
makedumpfile (Ubuntu)
Status tracked in Eoan
Xenial
High
Guilherme G. Piccoli
Bionic
High
Guilherme G. Piccoli
Cosmic
High
Guilherme G. Piccoli
Disco
High
Guilherme G. Piccoli
Eoan
High
Guilherme G. Piccoli

Bug Description

[Impact]
* Kdump command-line include an obsolete "nousb" parameter by default, which can cause a misimpression: users will think they are not booting with USB, but they are.

* Since kernel v4.5, the correct parameter to disable USB subsystem initialization is "usbcore.nousb" always (instead of "nousb" in case the subsystem is built-in). This was changed by commit 097a9ea0e48 ("usb: make "nousb" a clear module parameter").

* USB may be pretty essential in case for example kdump users need to decrypt a disk under LUKS, and there's only an USB keyboard connected to the system. Given the option is innocuous since Bionic, we should just drop it to prevent confusion.

[Test Case]

1) Deploy a Disco VM e.g. with uvt-kvm
2) Install the kdump-tools package
3) Run `kdump-config test`and check for the 'nousb' parameter:

$ kdump-config test
...
kexec command to be used:
  /sbin/kexec -p --command-line="BOOT_IMAGE=/boot/vmlinuz-4.15.0-45-generic root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0 nr_cpus=1 systemd.unit=kdump-tools.service irqpoll nousb ata_piix.prefer_ms_hyperv=0" /var/lib/kdump/vmlinuz

[Regression Potential]

The regression potential is extremely low, since the "nousb" parameter is not used since Bionic although is there. Any bugs we would have by changing this are still valid by not removing the option - the semantics with or without "nosub" is the same since from Bionic.

NOTICE we won't change Xenial, it can use kernel 4.4 which indeed disables USB by taking the "nousb" parameter.

Tags: seg Edit Tag help
affects: linux (Ubuntu) → makedumpfile (Ubuntu)
Changed in makedumpfile (Ubuntu Cosmic):
status: New → Confirmed
Changed in makedumpfile (Ubuntu Bionic):
status: New → Confirmed
Changed in makedumpfile (Ubuntu Xenial):
status: New → Confirmed
Changed in makedumpfile (Ubuntu Cosmic):
importance: Undecided → High
Changed in makedumpfile (Ubuntu Bionic):
importance: Undecided → High
Changed in makedumpfile (Ubuntu Xenial):
importance: Undecided → High
assignee: nobody → Guilherme G. Piccoli (gpiccoli)
Changed in makedumpfile (Ubuntu Bionic):
assignee: nobody → Guilherme G. Piccoli (gpiccoli)
Changed in makedumpfile (Ubuntu Cosmic):
assignee: nobody → Guilherme G. Piccoli (gpiccoli)
Changed in makedumpfile (Ubuntu Xenial):
assignee: Guilherme G. Piccoli (gpiccoli) → Heitor R. Alves de Siqueira (halves)
Changed in makedumpfile (Ubuntu Bionic):
assignee: Guilherme G. Piccoli (gpiccoli) → Heitor R. Alves de Siqueira (halves)
Changed in makedumpfile (Ubuntu Cosmic):
assignee: Guilherme G. Piccoli (gpiccoli) → Heitor R. Alves de Siqueira (halves)
Changed in makedumpfile (Ubuntu Disco):
assignee: Guilherme G. Piccoli (gpiccoli) → Heitor R. Alves de Siqueira (halves)
description: updated
description: updated
description: updated

The attachment "debdiff for disco" seems to be a debdiff. The ubuntu-sponsors team has been subscribed to the bug report so that they can review and hopefully sponsor the debdiff. If the attachment isn't a patch, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are member of the ~ubuntu-sponsors, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issue please contact him.]

tags: added: patch
Eric Desrochers (slashd) on 2019-02-19
Changed in makedumpfile (Ubuntu Disco):
status: Confirmed → In Progress
Changed in makedumpfile (Ubuntu Cosmic):
status: Confirmed → In Progress
Changed in makedumpfile (Ubuntu Bionic):
status: Confirmed → In Progress
Changed in makedumpfile (Ubuntu Xenial):
status: Confirmed → In Progress

Have you seen this cause any issue when kdumping from bionic or any releases later than xenial?

Because we should not disable usb, and I would apply the opposite fix and just remove "nousb" from the command line.

The reason for this is supporting kdump on encrypted systems, where the user must type a password and use a USB keyboard.

Cascardo.

Changed in makedumpfile (Ubuntu Disco):
status: In Progress → Opinion

Thanks for bringing that up, Cascardo. That was one scenario we didn't consider, and you're right about it causing problems for users with encrypted systems.

It does seem more sensible to just remove the 'nousb' option in this case, since this parameter has no effect in recent kernels. I'll respin the patches and change this LP to better reflect this.
Thanks!

summary: - Replace "nousb" option in kdump command-line for the newer
- "usbcore.nousb"
+ Remove obsolete "nousb" option in kdump command-line for newer kernels
description: updated
Simon Quigley (tsimonq2) wrote :

Unsubscribing the Ubuntu Sponsors Team as there is nothing to sponsor.

tags: removed: patch sts
tags: added: seg
Changed in makedumpfile (Ubuntu Xenial):
status: In Progress → Won't Fix
Changed in makedumpfile (Ubuntu Disco):
status: Opinion → Confirmed
Changed in makedumpfile (Ubuntu Eoan):
status: Opinion → Confirmed
Changed in makedumpfile (Ubuntu Xenial):
assignee: Heitor Alves de Siqueira (halves) → Guilherme G. Piccoli (gpiccoli)
Changed in makedumpfile (Ubuntu Bionic):
assignee: Heitor Alves de Siqueira (halves) → Guilherme G. Piccoli (gpiccoli)
Changed in makedumpfile (Ubuntu Cosmic):
assignee: Heitor Alves de Siqueira (halves) → Guilherme G. Piccoli (gpiccoli)
Changed in makedumpfile (Ubuntu Disco):
assignee: Heitor Alves de Siqueira (halves) → Guilherme G. Piccoli (gpiccoli)
Changed in makedumpfile (Ubuntu Eoan):
assignee: Heitor Alves de Siqueira (halves) → Guilherme G. Piccoli (gpiccoli)
description: updated
Guilherme G. Piccoli (gpiccoli) wrote :

This is the debdiff containing the proposed solution for this LP.
I'd like to thanks specially Cascardo and Heitor for the fruitful discussions with regards the direction we should take in this LP.

Changed in makedumpfile (Ubuntu Cosmic):
status: In Progress → Confirmed
Changed in makedumpfile (Ubuntu Eoan):
status: Confirmed → In Progress
Changed in makedumpfile (Ubuntu Bionic):
status: In Progress → Confirmed
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