[Bug 1869792] Re: [MIR] u-boot-rpi

Wed Apr 1 15:57:42 UTC 2020

On Wed, Apr 1, 2020 at 2:05 PM Christian Ehrhardt  <
1869792 at bugs.launchpad.net> wrote:
<snip>

> I agree that we should promote the package as well.
>

Excellent!

<snip>

> @David:
> - the package appears to get regular updates/fixes by the foundations team
> - upstream releases ~quarterly
> - it might be too late for the brand new 2020.04~rc4, but what is the
> reason to not update to 19.10 or 20.01?
> - Debian has 20.01 in testing and 20.04 in testing, so their speed is fast
> - Is there an active maintenance and update policy in place or is it
> randomly updated as needed?
>

This also ties in to why we haven't (yet) updated to 19.10: at present,
most of the effort in Eoan and Focal regarding the Pi platform has been
around the boot sequence (and in particular, ensuring compatibility of the
hardware with it). Testing is at least partially manual (as the Pi 4 has
proved incompatible with the hardware used in the lab to provide SD images
automatically, leading to a labor-intensive process of flashing and
changing cards for testing). Until the testing process can be automated,
we're extremely reticent to change major components (due to the effort
involved in re-testing) unless there's some tangible benefit in the new
version.

I'm not aware of an official update policy for the package, but I do keep
track of the upstream releases and check the changelog on (non-rc-)
releases (though unfortunately upstream's attitude to changelogs is "our
changelog can be generated from our git log" ... which largely explains why
I don't bother with the rc- releases; it usually takes a full day to trawl
through the generated thing!)

> - sometimes packages tend to be outdated by accruing to much delta that is
> hard to rebase&maintain; It seems the packaging was split mid last year on
> 2019.04+dfsg-2ubuntu1 and not rebase d since then. Might I ask about how
> well upstreaming to Debian works (links to some examples would be nice).
> I'd wan't to avoid that this package seems to be "ok now" but we can expect
> it to rot away for the reasons that inhibit regular maintenance mentioned
> above.
>

The bulk of our (and indeed Debian's own) delta appears to be for specific
hardware support (e.g. pi4 in our case), or for customizing the
configuration of u-boot to a particular distro (our other pi patches, and
the nitrogen6x patch). The latter style of patches (configuration
customization) I wouldn't expect to migrate because they'll be specific to
Ubuntu (or to Debian as the case may be).

The Pi4 code patches we apply to 2019.07 (d/p/rpi4.patch) have already made
it upstream to the u-boot project (in 2019.10) so those should disappear on
the next rebase. The rest of the Pi patches (d/p/rpi-board-dt.patch and
d/p/rpi2-rpi3-config-tweaks.patch) have to do with customizing the default
configuration for Ubuntu (the second style of patches that I wouldn't
expect to migrate), as are the nitrogen patches. In other words, I don't
think there's any delta we currently carry that a) hasn't already made it
upstream or b) wouldn't be relevant to upstream.

> To be clear I don't request to do these updates for Focal (it is too
> late), but I'd want to see some reassurance that this is under control
> and e.g. will get a rebase soon once 20.10 opens.
>

We should do, if only to get the reduced delta from the merge of the pi4
patches upstream.

> Marking incomplete until this is clarified.
>
> Note:
> If the above is ok (I assume it will be) we can hand over to security
> since the old bug had no explicit security check as far as I can see and as
> you outlined other binary packages of the same source have known CVEs I'd
> want security to:
> a) review for u-boot-rpi
> b) state that it is ok to add this to main with known CVEs in other
> binaries of the package (not that this might e.g. break their CVE tracking)
>

Sounds good!

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https://bugs.launchpad.net/bugs/1869792

Title:
  [MIR] u-boot-rpi

Status in u-boot package in Ubuntu:
  Incomplete

Bug description:
  [Availability]
  The package is already in universe.

  [Rationale]
  The package is in use in the boot sequence on all supported Raspberry Pi images, both classic and core.

  [Security]
  While there are (recent) open CVEs against u-boot, none appear relevant to the RPi port specifically. Notably:

  * CVE-2020-8432 deals with a double-free in cmd/gpt.c; GPT_CMD is not
  enabled in our rpi related u-boot configuration (because the pi does
  not support GUID partition tables).

  * CVE-2020-10648 deals with bypassing verified boot restrictions on
  FIT images; we don't use FIT u-boot images on our pi builds.

  * CVE-2019-16258 deals with attackers gaining root access by
  manipulating the u-boot console via UART; there's no expectation of
  boot security against physical access to a pi so this is irrelevant.

  * CVE-2019-14192..14204 deal with stack-based overflows against NFS
  and RPC commands. While our u-boot-rpi build does include NFS
  commands, they are not used in our boot scripts.

  All further CVEs deal with versions prior to 2019.07 (the current
  version in focal). Although it is clear vulnerabilities are reported
  with some regularity against the package, it is also evident that
  upstream responds rapidly to such reports and that many don't apply to
  our usage of the package on the pi. Furthermore, the pi is a
  relatively "open" platform with little expectation of security against
  direct physical access (after all, the storage is removable and
  unencrypted) which negates several of the reported vulnerabilities.

  [Quality assurance]
  As mentioned above, the package is already in active use in the Pi boot sequence. There are no outstanding bugs which significantly affect the usability (i.e. our images boot successfully on all supported pi models) and no important bugs open.

  There is no meaningful test suite included in the package, but then
  for a bootloader dealing with a novel platform the ultimate test is
  "does it boot?", and each update of the package is extensively
  (manually) tested against the supported models.

  The current version of the package does build-depend against python2.
  This is an issue noted in an upstream report (Debian: #943273),
  corrected in the current version in sid
  (https://salsa.debian.org/debian/u-boot/-/commit/f8a0fc63adbe13e0a3365af9b03e8315f1328913),
  and hence will be corrected next time our package is synced with
  upstream.

  [UI standards]
  The sole interactive element is the u-boot console which is only expected to be used in the circumstance that the system is un-bootable. This is (hopefully!) a sufficiently rare circumstance that the lack of localization does not pose an issue (further, it's hard to see how a bootloader could be localized given it is running prior to the OS starting and thus without knowledge of user configuration).

  [Dependencies]
  The sole runtime dependency is "awk", the installation candidates for which (gawk or mawk) are already present in main.

  [Standards compliance]
  The package installs its binaries under /usr/lib which may seem odd for something essential to booting the system but this is merely a "storage location". These binaries are then copied (via postinst currently, hopefully in future via flash-kernel) to the more appropriate /boot hierarchy.

  [Maintenance]
  The package is maintained by the Ubuntu Foundations team.

  [Background information]
  As mentioned above the package is already in active use on all our Raspberry Pi images (both classic and core). It's only recently that it was brought to my attention that the package isn't in main already. The package is essential to both the classic and core boot experiences: in the classic case for providing unpacking duties for compressed kernels, and in the core case for handling A/B boot states (neither of these facilities is currently supported by the pi's own firmware bootloader).

  This package is currently pulled into the images via the "pi-gadget"
  (https://github.com/snapcore/pi-gadget) snap which forms the basis of
  both the classic and core pi images.

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