CVE-2023-53625
Description
A NULL pointer dereference was found in the Linux kernel Intel i915 graphics driver's virtual GPU debugfs cleanup handling. A local user with privileges to unbind the i915 driver can trigger driver removal on systems with active virtual GPU instances, causing the cleanup path to attempt removing debugfs entries after the debugfs root has already been destroyed, which results in a NULL pointer dereference and denial of service through kernel crash.
Statement
The issue arises because of incorrect ordering in the driver removal sequence. When the i915 driver with GVT-g (GPU virtualization) support is unbound, the cleanup proceeds through multiple stages: driver removal, MDEV (mediated device) unregistration, and vGPU destruction. During vGPU destruction, the code unconditionally calls intel_gvt_debugfs_remove_vgpu() to clean up debugfs entries. However, at this point in the removal sequence, the DRM minor's debugfs root may have already been torn down. When debugfs_remove() attempts to lock the inode semaphore to recursively remove entries, it dereferences a NULL pointer (address 0x150, an offset into the destroyed debugfs inode structure), causing an immediate kernel oops. This occurs reliably on any system using GVT-g when the driver is unbound while virtual GPUs exist. The impact is strictly availability—the system crashes during driver removal. There is no memory corruption, information disclosure, or path to privilege escalation; the NULL dereference happens in lock acquisition code before any potentially dangerous operations could occur.
Mitigation
To mitigate this issue, prevent the kvmgt module from loading. See https://access.redhat.com/solutions/41278 for instructions on blacklisting kernel modules.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | 5.5 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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