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[Launchpad Bug Tracker <1800562@xxxxxxxxxxxxxxxxxx>]

You have been subscribed to a public bug by Eric Desrochers (slashd):

[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: makedumpfile (Ubuntu)
     Importance: High
     Assignee: Heitor R. Alves de Siqueira (halves)
         Status: Confirmed

** Affects: makedumpfile (Ubuntu Xenial)
     Importance: High
     Assignee: Heitor R. Alves de Siqueira (halves)
         Status: Confirmed

** Affects: makedumpfile (Ubuntu Bionic)
     Importance: High
     Assignee: Heitor R. Alves de Siqueira (halves)
         Status: Confirmed

** Affects: makedumpfile (Ubuntu Cosmic)
     Importance: High
     Assignee: Heitor R. Alves de Siqueira (halves)
         Status: Confirmed

** Affects: makedumpfile (Ubuntu Disco)
     Importance: High
     Assignee: Heitor R. Alves de Siqueira (halves)
         Status: Confirmed


** Tags: sts
-- 
Replace "nousb" option in kdump command-line for the newer "usbcore.nousb"
https://bugs.launchpad.net/bugs/1800562
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