In the Linux kernel, the following vulnerability has been resolved: agp/amd64: Fix broken error propagation in agpamd64probe() 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 amd64fetchsize() when attempting to dereference the pointer returned by nodetoamdnb(0). The root cause of this crash is broken error propagation in agpamd64probe(): When no AMD northbridges are found, cachenbs() 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 agpaddbridge(), which invokes amd64fetchsize(). Since the hardware does not exist, nodetoamdnb(0) returns NULL, leading to a General Protection Fault (GPF) when accessing its ->misc member. Fix the issue by correcting the error check in agpamd64probe() to abort properly when cachenbs() returns any negative error code. This prevents the driver from erroneously proceeding without hardware, thereby avoiding the subsequent NULL pointer dereference at its source.