CVE-2024-56745

What it actually does

Memory leak in reset_method_store() where kstrndup-allocated string assigned to 'options' is not freed after strsep() sets the pointer to NULL on final token, causing the subsequent kfree to have no effect.

Why it matters to the business

Repeated invocation of the affected PCI reset method store path can gradually exhaust kernel memory, leading to system instability or denial of service on long-running systems; the affected qemu package on Ubuntu 14.04 LTS increases exposure for legacy virtualization environments.

How an attack unfolds

An attacker with local access triggers repeated writes to the PCI reset_method sysfs attribute; each call leaks the duplicated string because strsep exhausts the pointer, allowing gradual memory consumption without any external network activity or named threat actor involvement.

How to fix it

Upgrade the affected qemu package on Ubuntu 14.04 LTS to version 2.0.0+dfsg-2ubuntu1.30 or later; apply the corresponding Linux kernel patch that introduces a separate tmp_options pointer to preserve the original allocation for kfree.

How to confirm the fix worked

Confirm the running kernel or qemu package reports the fixed version string; exercise the reset_method_store code path while monitoring /proc/meminfo or slabinfo for absence of repeated leaks under sustained attribute writes.

Typical attack path

1. Obtain local unprivileged or privileged access on the target system
2. Locate and repeatedly write space-separated values to the PCI device reset_method attribute
3. Trigger the kstrndup + strsep path in reset_method_store multiple times
4. Observe gradual kernel memory depletion until resource limits or OOM conditions occur

How to detect it

Search kernel logs and audit trails for repeated accesses to PCI sysfs reset_method attributes; monitor slab or kmalloc leak detectors for allocations originating from reset_method_store without corresponding frees.

What your security team should do

• Prioritize patching legacy Ubuntu 14.04 qemu installations within normal change windows given the low EPSS and non-KEV status
• Add kernel memory leak detection tooling to CI pipelines for PCI sysfs paths
• Review any custom scripts that write to reset_method attributes and reduce frequency where possible