Linux Kernel AGP AMD64 Driver NULL Deref due to Faulty Error Propagation
CVE-2026-53325 Published on June 29, 2026
agp/amd64: Fix broken error propagation in agp_amd64_probe()
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.
Products Associated with CVE-2026-53325
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Affected Versions
Linux:- Version a32073bffc656ca4bde6002b6cf7c1a8e0e22712 and below 53483a9f4ee9eeb18aa866ec16cce79e136987e1 is affected.
- Version a32073bffc656ca4bde6002b6cf7c1a8e0e22712 and below 0aa9b27c454c53074cde592eaceb442d30341585 is affected.
- Version a32073bffc656ca4bde6002b6cf7c1a8e0e22712 and below cefe535a60a2e00e09f4b2689b0c8ffc6912459a is affected.
- Version a32073bffc656ca4bde6002b6cf7c1a8e0e22712 and below b08472db93b1ccff84a7adec5779d47f0e9d3a30 is affected.
- Version 2.6.18 is affected.
- Before 2.6.18 is unaffected.
- Version 6.18.37, <= 6.18.* is unaffected.
- Version 7.0.14, <= 7.0.* is unaffected.
- Version 7.1.2, <= 7.1.* is unaffected.
- Version 7.2-rc1, <= * is unaffected.