Canonical was forced to release a second round of Ubuntu updates that address the recently disclosed CPU vulnerabilities after some users complained that their systems no longer booted after installing the initial patches.
On January 9, Canonical released Ubuntu updates designed to mitigate Spectre and Meltdown, two recently disclosed attack methods that work against processors from Intel, AMD, ARM, Qualcomm and IBM. The Linux kernel updates mitigate the vulnerabilities that allow the Meltdown (CVE-2017-5754) and Spectre (CVE-2017-5753 and CVE-2017-5715) attacks.
Shortly after the kernel was updated to version 4.4.0-108, some Ubuntu users started complaining that their systems had failed to boot. Restoring the system to an earlier version apparently resolved the problem.
The updates released by Microsoft in response to the CPU flaws also caused problems, but only for users with some older AMD processors. The company has decided to no longer deliver the updates to AMD devices until compatibility issues are resolved. In the case of Ubuntu, however, the update has affected users with Intel processors.
Canonical has confirmed that the fix for the Meltdown vulnerability introduced a regression that prevented systems from booting successfully. The issue has been addressed with the release of new updates that deliver version 184.108.40.206 of the kernel.
Many affected users have confirmed that their systems boot properly after updating to 4.4.0-109. While it’s unclear how many devices have been hit, Canonical’s advisories mention “a few systems.”
Affected tech firms started announcing the availability of patches and workarounds for the Spectre and Meltdown vulnerabilities shortly after the flaws were disclosed by researchers. The latest major companies to release mitigations are IBM, whose POWER processors and Power Systems servers are impacted, and NVIDIA, which released updates for GPU display drivers and other products to help mitigate the CPU issues.
Meltdown and Spectre allow malicious applications to bypass memory isolation mechanisms and access passwords, photos, documents, emails, and other sensitive information. Patches for the underlying vulnerabilities may introduce significant performance penalties.