CVE-2024-50017

What it actually does

The ident_pud_init function in x86 memory management can use 1GB pages for identity mappings even when the request covers only part of a GB page, resulting in mapping of additional address ranges including BIOS-reserved regions and enabling processor speculation into those areas.

Why it matters to the business

Unexpected system halts on UV hardware can cause operational downtime and require restarts, impacting availability of systems using affected kernel versions.

How an attack unfolds

An attacker with the ability to influence memory mapping requests during kernel initialization or through specific workloads on UV systems could trigger the over-mapping, leading to speculation-induced halts. However, given the nature, it may manifest as a stability issue rather than direct remote exploitation.

How to fix it

Update the Linux kernel to a version containing commit d113f9723f2bfd9c6feeb899b8ddbee6b8a6e01f or later fixed versions such as tcpdump 4:4.9.3-2.el8 if applicable.

How to confirm the fix worked

Verify the kernel source includes the change to use GB pages only for full GB requests and check for the commit hash in the running kernel or source.

Typical attack path

1. Identify vulnerable kernel version
2. Trigger conditions for identity map creation with partial GB pages
3. Cause speculation into reserved regions
4. Induce system halt

How to detect it

Review kernel logs for signs of system halts related to memory mapping or speculation on UV systems; check boot logs for identity mapping behavior.

What your security team should do

• Prioritize kernel updates on affected systems especially UV hardware
• Monitor for system halts post-update
• Test in staging environments