** Description changed:
[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
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https://bugs.launchpad.net/bugs/1800562
Title:
Replace "nousb" option in kdump command-line for the newer
"usbcore.nousb"
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