grub2-mkconfig crashes with "free(): invalid next size (normal)" message or fails with "error: environment block too small"

Environment

• Red Hat Enterprise Linux 8
  • grub2 prior to version 2.02-90.el8

Issue

• When executing grub2-mkconfig to rebuild the Grub menu, the command dumps core and print the following message

  # grub2-mkconfig -o /etc/grub2.cfg
  Generating grub configuration file ...
  free(): invalid next size (normal)
  /etc/grub.d/10_linux: line 128: PID Aborted                 (core dumped)
  

• When executing grub2-mkconfig to rebuild the Grub menu, the command fails with the following message

  # grub2-mkconfig -o /etc/grub2.cfg
  Generating grub configuration file ...
  /usr/bin/grub2-editenv: error: environment block too small.
  

Resolution

• Red Hat investigated the issue under This content is not included.BZ 1761496 - grub2-editenv segfaults when called through grub2-mkconfig.  A fix was released on 2020-11-03 through grub2 bug fix and enhancement update RHBA-2020:4513.

Workaround

1. Delete current /boot/grub/grubenv file

   # rm /boot/grub/grubenv
   

2. Disable BLS in Grub's configuration file

   # sed -i "s/GRUB_ENABLE_BLSCFG=true/GRUB_ENABLE_BLSCFG=false/" /etc/default/grub
   

3. Rebuild the Grub menu

   # grub2-mkconfig -o /etc/grub2.cfg
   

   Note: on UEFI file systems, specify /etc/grub2-efi.cfg instead of /etc/grub2.cfg

Root Cause

• Grub corrupts the /boot/grub/grubenv file or file is too big to be handled properly

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