On Thu, 2022-05-12 at 15:01 +0800, Coiby Xu wrote:

Currently, a problem faced by arm64 is if a kernel image is signed by a
MOK key, loading it via the kexec_file_load() system call would be
rejected with the error "Lockdown: kexec: kexec of unsigned images is
restricted; see man kernel_lockdown.7".

This happens because image_verify_sig uses only the primary keyring that
contains only kernel built-in keys to verify the kexec image.

From the git history it's clear that .platform keyring was upstreamed
during the same open window as commit 732b7b93d849 ("arm64: kexec_file:
add kernel signature verification support").   Loading the MOK keys
onto the .platform keyring was upstreamed much later.  For this reason,
commit 732b7b93d849 only used keys on the  .builtin_trusted_keys
keyring.   This patch is now addressing it and the newly upstreamed
.machine keyring.

Only using the .builtin_trusted_keys is the problem statement, which
should be one of the first lines of the patch description, if not the
first line.

This patch allows to verify arm64 kernel image signature using not only
.builtin_trusted_keys but also .platform and .secondary_trusted_keys
keyring.

Please remember to update this to include the .machine keyring.

Fixes: 732b7b93d849 ("arm64: kexec_file: add kernel signature verification support")

Since the MOK keys weren't loaded onto the .platform keyring until much
later, I would not classify this as a fix.

thanks,

Mimi


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