CVE-2026-53325agp/amd64: Fix broken error propagation in agp_amd64_probe()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ce800993af477fc24187349c6a20d3073140b759
• https://git.kernel.org/stable/c/1d7d45050e14083c1de1460c93f4063c1f0bca7b
• https://git.kernel.org/stable/c/3e844a63668d1c3d10a9d347d7ebf161b2f91c84
• https://git.kernel.org/stable/c/eb045714bc6a2bbb0befb7a31b996a196e188869
• https://git.kernel.org/stable/c/564b3b3f6565313eb6fa5355ffd037d6fb27897f
• https://git.kernel.org/stable/c/53483a9f4ee9eeb18aa866ec16cce79e136987e1
• https://git.kernel.org/stable/c/0aa9b27c454c53074cde592eaceb442d30341585
• https://git.kernel.org/stable/c/cefe535a60a2e00e09f4b2689b0c8ffc6912459a
• https://git.kernel.org/stable/c/b08472db93b1ccff84a7adec5779d47f0e9d3a30
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html