EBG config partitions on other disk break EBG userspace components

[MOESSBAUER, Felix]

Dear Devs,

when having multiple disks in a system with ebg config partitions each,
the libebgenv is not able to locate the correct environment and instead
just fails with the following error:

"Error, there are more than 2 config partitions."

The EBG EFI part properly probes the current boot device and only
searches for EBG configs on that device. However, the userspace part
(which is also used by swupdate) does not have this logic and simply
scans all blockdevices in `/dev/`.

In general, wildly guessing and probing devices in `/dev/` should be
avoided, as this likely leads to unwanted side-effects. We must not
make any guesses about the content of a device that is potentially not
under our control.

I temporarily solved this issue in the downstream project by hard-
coding the expected partition into the probe_config_partition function,
but this is not a generic solution.

Best regards,
Felix

[Jan Kiszka]

On 20.09.23 05:12, 'MOESSBAUER, Felix' via EFI Boot Guard wrote:
> Dear Devs,
>
> when having multiple disks in a system with ebg config partitions each,
> the libebgenv is not able to locate the correct environment and instead
> just fails with the following error:
>
> "Error, there are more than 2 config partitions."
>
> The EBG EFI part properly probes the current boot device and only
> searches for EBG configs on that device. However, the userspace part
> (which is also used by swupdate) does not have this logic and simply
> scans all blockdevices in `/dev/`.

Then let's fix it, patches welcome.

>
> In general, wildly guessing and probing devices in `/dev/` should be
> avoided, as this likely leads to unwanted side-effects. We must not
> make any guesses about the content of a device that is potentially not
> under our control.

There are use cases, see e.g. docs/RECOVERY.md.

Jan

>
> I temporarily solved this issue in the downstream project by hard-
> coding the expected partition into the probe_config_partition function,
> but this is not a generic solution.
>
> Best regards,
> Felix
>

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