CVE-2023-53789

The vulnerability resides in the AMD IOMMU driver's page fault handler (report_iommu_fault). When an IOMMU page fault occurs for a device group whose domain has not been set up, the handler assumes the domain pointer is valid and dereferences it without a NULL check, leading to a kernel NULL pointer dereference and system crash [1].

An attacker can exploit this by causing an IOMMU page fault on a device whose domain is uninitialized. This may occur due to misconfiguration, hardware issues, or deliberate triggering via a malicious or misbehaving device. The attack requires local access to the system and the ability to generate such faults, but no special privileges beyond that.

The impact is a denial of service: the kernel crashes with a NULL pointer dereference, as shown in the sample log where the AMD-Vi interrupt handler thread triggers an Oops. This can disrupt system availability.

The fix is implemented in Linux kernel commit be8301e2d5a8b95c04ae8e35d7bfee7b0f03f83a, which adds a check for a valid domain before dereferencing and logs an appropriate error message instead of crashing [1]. Users should apply kernel updates containing this patch.