Replace "nousb" option in kdump command-line for the newer "usbcore.nousb"

Bug #1800562 reported by Guilherme G. Piccoli on 2018-10-29
16
This bug affects 2 people
Affects Status Importance Assigned to Milestone
makedumpfile (Ubuntu)
Status tracked in Disco
Xenial
High
Heitor R. Alves de Siqueira
Bionic
High
Heitor R. Alves de Siqueira
Cosmic
High
Heitor R. Alves de Siqueira
Disco
High
Heitor R. Alves de Siqueira

Bug Description

[Impact]
Crash kernels come up with the usb subsystem enabled, even when it should be disabled by default.

[Description]
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").

We need to take this into account in kdump-tools, or else we may boot with USB in kdump even the command-line saying the opposite.

This affects Xenial onwards, since the system may be running an HWE or other supported v4.5+ kernel.

[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 'usbcore.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 very low, since it doesn't need any changes in makedumpfile and we're only adding a parameter on the crashkernel cmdline.
According to kernel documentation [0], unknown parameters will be ignored if they contain a dot (usbcore.nousb), so this change should have no impact on v4.4 and earlier kernels.
Nonetheless, the fix will be tested with autopkgtests and normal kdump use-case scenarios.

[0] https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.rst

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.

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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
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