Bug 2494092 (CVE-2026-53325)

Summary: CVE-2026-53325 kernel: agp/amd64: Fix broken error propagation in agp_amd64_probe()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: low    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's AMD64 AGP (Accelerated Graphics Port) driver. This vulnerability occurs in virtualized environments lacking a physical AMD northbridge. Due to incorrect error handling, the driver attempts to initialize without the required hardware, leading to a NULL pointer dereference and causing the system to crash. This can result in a Denial of Service (DoS) for the affected system.
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Description OSIDB Bzimport 2026-06-29 06:02:00 UTC 
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.
Comment 1 Mauro Matteo Cascella 2026-06-29 07:39:49 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062926-CVE-2026-53325-b162@gregkh/T