CVE-2022-48769

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

efi: runtime: avoid EFIv2 runtime services on Apple x86 machines

Aditya reports [0] that his recent MacbookPro crashes in the firmware

when using the variable services at runtime. The culprit appears to be a

call to QueryVariableInfo(), which we did not use to call on Apple x86

machines in the past as they only upgraded from EFI v1.10 to EFI v2.40

firmware fairly recently, and QueryVariableInfo() (along with

UpdateCapsule() et al) was added in EFI v2.00.

The only runtime service introduced in EFI v2.00 that we actually use in

Linux is QueryVariableInfo(), as the capsule based ones are optional,

generally not used at runtime (all the LVFS/fwupd firmware update

infrastructure uses helper EFI programs that invoke capsule update at

boot time, not runtime), and not implemented by Apple machines in the

first place. QueryVariableInfo() is used to 'safely' set variables,

i.e., only when there is enough space. This prevents

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References