[Bug 2039172] Re: grub 2.12~rc1 fails to load files from large directories on XFS

[Nick Rosbrook]

** Description changed:

  [Impact]
  Multi-extent directories are not parsed correctly by grub's XFS code in 2.12~rc1, preventing it from loading files from directories with too many entries, such as the grub module directory.
  
  This should only affect BIOS systems as they need to load the core grub
  modules from the module directory, whereas UEFI systems have them
  embedded in the ESP EFI image.
  
  [Test plan]
- TBD
+ 
+ There are three scenarios we should test:
+ 
+ (1) BIOS system with XFS /boot
+ (2) UEFI arm64 with grub and XFS /boot
+ (3) A "normal" system that should not hit this bug
+ 
+ Test upgrades from Lunar to Mantic for the above scenarios. On systems
+ that match (1) or (2), the upgrade should be prevented early on with a
+ message linking to this bug report. For (3), the upgrade should proceed
+ as normal.
  
  [Where problems could occur]
- TBD
+ The two risks here are (1) missing a case where we should block upgrade, and (2) preventing an upgrade in a case where we should not. The unit tests included in the patch attempt to mitigate this risk.
+ 
+ Any issues would probably come from logic errors in the code that parses
+ /proc/mounts, or in the arm64 case, the logic for checking if grub is
+ installed.

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https://bugs.launchpad.net/bugs/2039172

Title:
  grub 2.12~rc1 fails to load files from large directories on XFS

Status in grub2 package in Ubuntu:
  Triaged
Status in ubuntu-release-upgrader package in Ubuntu:
  Triaged
Status in grub2 source package in Mantic:
  New
Status in ubuntu-release-upgrader source package in Mantic:
  Triaged
Status in grub2 source package in Noble:
  Triaged
Status in ubuntu-release-upgrader source package in Noble:
  Triaged
Status in grub2 package in Debian:
  Confirmed

Bug description:
  [Impact]
  Multi-extent directories are not parsed correctly by grub's XFS code in 2.12~rc1, preventing it from loading files from directories with too many entries, such as the grub module directory.

  This should only affect BIOS systems as they need to load the core
  grub modules from the module directory, whereas UEFI systems have them
  embedded in the ESP EFI image.

  [Test plan]

  There are three scenarios we should test:

  (1) BIOS system with XFS /boot
  (2) UEFI arm64 with grub and XFS /boot
  (3) A "normal" system that should not hit this bug

  Test upgrades from Lunar to Mantic for the above scenarios. On systems
  that match (1) or (2), the upgrade should be prevented early on with a
  message linking to this bug report. For (3), the upgrade should
  proceed as normal.

  [Where problems could occur]
  The two risks here are (1) missing a case where we should block upgrade, and (2) preventing an upgrade in a case where we should not. The unit tests included in the patch attempt to mitigate this risk.

  Any issues would probably come from logic errors in the code that
  parses /proc/mounts, or in the arm64 case, the logic for checking if
  grub is installed.

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