CVE-2026-53325

In the Linux kernel, the following vulnerability has been resolved:

agp/amd64: Fix broken error propagation in agp_amd64_probe()

A NULL pointer dereference was observed in the AMD64 AGP driver when

running in a virtualized environment (e.g. qemu/kvm) without a physical

AMD northbridge. The crash occurs in amd64_fetch_size() when attempting

to dereference the pointer returned by node_to_amd_nb(0).

The root cause of this crash is broken error propagation in

agp_amd64_probe(): When no AMD northbridges are found, cache_nbs()

correctly returns -ENODEV. However, the probe function erroneously

checks the return value against exactly -1, rather than < 0.

As a result, the hardware absence error is masked, allowing the driver

to improperly proceed with initialization. It eventually calls

agp_add_bridge(), which invokes amd64_fetch_size(). Since the hardware

does not exist, node_to_amd_nb(0) returns NULL, leading to a General

Protection Fault (GPF) when accessing its ->misc member.

Fix the issue by correcting the error check in agp_amd64_probe() to

abort properly when cache_nbs() returns any negative error code. This

prevents the driver from erroneously proceeding without hardware, thereby

avoiding the subsequent NULL pointer dereference at its source.