CVE-2024-49856 x86/sgx: Fix deadlock in SGX NUMA node search
A deadlock in the Linux kernel SGX NUMA node search causes a soft lockup when EPC sections are unavailable, requiring specific firmware configurations.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-49856?
CVE-2024-49856 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 Oct 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
x86/sgx: Fix deadlock in SGX NUMA node search
When the current node doesn't have an EPC section configured by firmware and all other EPC sections are used up, CPU can get stuck inside the while loop that looks for an available EPC page from remote nodes indefinitely, leading to a soft lockup. Note how nid_of_current will never be equal to nid in that while loop because nid_of_current is not set in sgx_numa_mask.
Also worth mentioning is that it's perfectly fine for the firmware not to setup an EPC section on a node. While setting up an EPC section on each node can enhance performance, it is not a requirement for functionality.
Rework the loop to start and end on *a* node that has SGX memory. This avoids the deadlock looking for the current SGX-lacking node to show up in the loop when it never will.
Weakness: CWE-835
Which versions are affected by CVE-2024-49856?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-49856?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-49856 being exploited?
There is no known exploitation of CVE-2024-49856 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-50709, AZL-50963, BELL-CVE-2024-49856, DEBIAN-CVE-2024-49856, GHSA-333m-q4jm-qjq4, UBUNTU-CVE-2024-49856.