Public bug reported:
[Impact]
Systems that use flash-kernel may end up installing the wrong kernel image.
`linux-version sort` can provide different answers depending on how it
is called (see Test Case). The stdin behavior appears to be a bug, and
this is the mode flash-kernel uses. So, for example, a user with an
arm64 u-boot system might end up booting 5.8.0-50-generic-64k instead of
the expected 5.8.0-50-generic if both are installed. There maybe
additional issues caused by this; for example, I found this with our
automation that tests kernels on various arm64 platforms in version
increasing order. Only after consulting logs did we realize that 64k
kernels were not ever getting booted because the tooling (which uses
argv mode) disagreed with the kernel installer (flash-kernel using stdin
mode) about which kernel should be the default.
[Test Case]
Using argv:
$ linux-version sort 5.8.0-50-generic 5.8.0-50-generic-64k
5.8.0-50-generic
5.8.0-50-generic-64k
Using stdin (incorrect):
$ cat versions.txt
5.8.0-50-generic
5.8.0-50-generic-64k
$ cat versions.txt | linux-version sort
5.8.0-50-generic-64k
5.8.0-50-generic
[Where Problems Could Occur]
An obvious place where problems could occur is if someone is relying on
rebooting into the kernel that is incorrectly being sorted greatest. For those
using only Ubuntu kernel packages, the only case I'm aware of is arm64 generic
vs. generic-64k case used in the examples above. The generic-64k flavor is
available in >= 20.10, as well as 20.04-hwe. ARM server users - those most
likely to want the generic-64k flavor - are very unlikely to be using
flash-kernel. The standard for ARM servers is UEFI firmware, which use GRUB and
are unaffected by this change. We found this on an old HP m400 platform which
is the only Ubuntu certified u-boot-based arm64 server, and is long out of
support.
** Affects: linux-base (Ubuntu)
Importance: Undecided
Status: New
** Affects: linux-base (Debian)
Importance: Unknown
Status: Unknown
** Bug watch added: Debian Bug tracker #987851
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=987851
** Also affects: linux-base (Debian) via
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=987851
Importance: Unknown
Status: Unknown
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https://bugs.launchpad.net/bugs/1926985
Title:
linux-version sort: argv and stdin behaviors differ
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