CVE-2023-52740

What it actually does

Race condition in powerpc/64s interrupt exit path where RFI and STF mitigation static branch can flip concurrently with MSR[EE|RI] tests, corrupting irq soft-mask state and leaving interrupts disabled or in inconsistent state, resulting in warnings and possible kernel crashes.

Why it matters to the business

Affected powerpc systems running the vulnerable kernel may experience unexpected crashes or degraded stability, potentially causing service outages on legacy Ubuntu 14.04 deployments until patched.

How an attack unfolds

An attacker with local code execution triggers interrupt exit sequences while concurrently switching security mitigations to race the static branch test, corrupting MSR and soft-mask state to induce warnings or crashes; no external or remote exploitation path is known and no threat actors have been observed using it.

How to fix it

Upgrade qemu packages on Ubuntu 14.04 LTS to version 2.0.0+dfsg-2ubuntu1.24 or later; apply the kernel fix that resolves the interrupt exit race with security mitigation switching.

How to confirm the fix worked

Confirm the installed qemu package version meets or exceeds 2.0.0+dfsg-2ubuntu1.24 and verify the kernel source no longer contains the concurrent branch test in interrupt exit paths.

Typical attack path

1. Obtain local execution on affected powerpc system
2. Trigger concurrent security mitigation switch during interrupt exit
3. Induce MSR/soft-mask corruption leading to kernel warning or crash

How to detect it

Review kernel logs for warnings originating from irq_64.c related to MSR or interrupt mask state on powerpc; examine crash dumps showing corrupted soft-mask or EE bit settings during interrupt replay.

What your security team should do

• Prioritize patching legacy Ubuntu 14.04 powerpc systems within standard maintenance windows
• Monitor kernel logs for irq_64.c warnings on powerpc hardware
• Remove or isolate unsupported Ubuntu 14.04 instances where feasible