Linux Rockchip VOP2 Fix Prevents Kernel Crash CVE-2025-38597

A subtle null-pointer check in the Linux DRM driver for Rockchip VOP2 has been fixed after security researchers and maintainers discovered a condition that can be trivially triggered on affected hardware to produce a sustained or persistent denial-of-service, tracked as CVE-2025-38597.

Background / Overview​

The vulnerability lives in the Linux kernel's Direct Rendering Manager (DRM) Rockchip VOP2 driver, the component responsible for managing display controller hardware on many Rockchip System-on-Chips (SoCs). VOP2 — the Video Output Processor 2 — exposes multiple windows or “planes” that map image buffers to hardware video ports. During driver probe, the code attempts to find a primary plane for each video port and later initializes the CRTC (display controller) using that plane. In certain configurations of Rockchip hardware (notably RK3576 variants), a port may legitimately lack a usable primary plane — for example when vp0 is already in use — and the driver previously did not check whether a primary plane had actually been found before calling drm_crtc_init_with_planes. The result: a null-pointer dereference that can crash the driver or kernel and cause high-impact availability loss.
Maintainers added a single, defensive check at the end of the window-iteration loop to fail probing cleanly if no primary plane is found for a given video port. The fix prevents the dereference and changes the failure mode from uncontrolled crashes to a deterministic, recoverable probe failure. This vulnerability was assigned CVE-2025-38597 and has been propagated into stable kernel trees and downstream distribution advisories.

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Technical deep dive: what went wrong and why it matters​

How VOP2, planes, and video ports interact​

VOP2 exposes a collection of windows (planes) that can be assigned to different video ports (vp0, vp1, vp2, etc.. Each plane has metadata describing the ports it supports and whether it is the primary plane for a port. The DRM core exposes APIs (such as drm_crtc_init_with_planes) that bind a CRTC to a pair of planes — a primary plane and an optional cursor/overlay plane.
The driver’s probe logic iterates windows to discover which window can act as the primary plane for each video port. Finding a primary plane is a precondition before calling drm_crtc_init_with_planes. If the driver mistakenly proceeds without confirming that a primary plane was actually found, drm_crtc_init_with_planes receives a null pointer for the primary plane argument. That null pointer dereference manifests later as a kernel oops or panic when the kernel attempts to use the missing plane structure.

Root cause​

• Missing defensive programming: the probe code assumed that a primary plane would always be discovered during iteration, and did not validate the pointer before use.
• Hardware configuration corner-case: certain SoC and board configurations (e.g., RK3576 with vp0 already in use) produce a valid runtime state where a video port has no usable primary window.
• Resulting failure mode: null-pointer dereference → kernel oops → process or whole-system instability or crash → denial-of-service (availability loss).

The fix​

Maintainers inserted a check after the window-iteration:

• If no primary plane is found for a video port, the driver now returns an error from probe (dev_err_probe with -ENOENT and an explanatory message) instead of proceeding and causing a null dereference.
• This converts an uncontrolled kernel fault into an explicit probe failure, which is far safer: the driver will not bind incorrectly configured hardware, and the kernel remains stable.

The fix is small in code size but important in behavior: defensive checks at hardware probe time are a common and effective way to avoid latent crashes.

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Affected systems and scope​

Hardware and drivers​

• Rockchip SoCs that use the VOP2 driver are the primary hardware affected. The RK3576 family was specifically highlighted because its port configuration surfaced the issue.
• Systems that use the kernel DRM rockchip VOP2 driver (drivers/gpu/drm/rockchip/rockchip_drm_vop2.c) and that present configurations where a video port can lack a primary plane are susceptible.

Software versions​

• The issue existed in kernels that included the original VOP2 driver implementation (the upstream driver added as part of the VOP2 support).
• Downstream distribution kernels vary in exposure: some older enterprise/stable branches may have received the fix in stable updates while several distributions and embedded vendors may still ship vulnerable kernel versions depending on their update cadence.
• Embedded devices, firmware images, Android builds, and appliances that use vendor-supplied kernels on Rockchip platforms can be vulnerable until the vendor applies the patch and ships a firmware/kernel update.

Attack vector and prerequisites​

• Attack vector: local. Exploitation typically requires local access to the system or the ability to trigger driver probe behavior (for example, by loading/unloading modules or manipulating hardware state or hot-plugging display hardware).
• Privileges: low. The vulnerability can be triggered without elevated privileges if a local user can cause the driver to re-probe or can interact with the DRM subsystem in ways that exercise the problematic path.
• Complexity: low. The condition is reproducible when the hardware/port configuration satisfies the missing primary plane condition; the added null dereference shows that a single incorrect code path is sufficient to crash the driver.

Impact​

• Confidentiality: None. The bug does not leak secrets or bypass access controls.
• Integrity: None. No elevation of privilege or arbitrary code execution is implied.
• Availability: High. A null-pointer dereference in kernel-space can crash the driver or kernel, causing a denial-of-service that is either sustained (while attack conditions persist) or persistent (if the kernel state is left unusable until a reboot or firmware update).

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Timeline and vendor response​

• The problematic driver behavior was identified and a patch was posted to the kernel mailing list and stable trees. Maintainers acknowledged and committed the fix into the stable kernel trees.
• Distribution security trackers and vendor advisories subsequently published entries describing the vulnerability and the patched status for their kernel packages. Multiple distribution security trackers categorized the issue as medium severity overall (because confidentiality and integrity are unaffected), with specific notes that availability impact is high.
• The fix was backported into stable kernel releases where maintainers judged it appropriate, and vendors were advised to include the change in their firmware and kernel updates.

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Detection and indicators of compromise (what to look for)​

Because CVE-2025-38597 is a denial-of-service via kernel null-pointer dereference, indicators are operational rather than stealthy.
Look for:

• Kernel oops/panic logs referencing rockchip/vop2, drm, or messages indicating "no primary plane for vp X" or similar probe errors.
• Repeated crashes or hung systems after display reconfiguration, hot-plug events, or after loading/unloading DRM modules.
• dmesg output containing stack traces with functions in drivers/gpu/drm/rockchip/rockchip_drm_vop2.c or drm_crtc_init_with_planes.
• Systems that crash only when specific displays or ports are used (e.g., using vp1 or vp2 while vp0 is active).

Operational detection steps:

• Run dmesg or check /var/log/kern.log for recent kernel oops and look for DRM/rockchip stack traces.
• Monitor system uptime correlated with display reconfiguration actions; frequent crashes after display events are a strong signal.
• For embedded devices, collect serial console logs from boot and during repro attempts; these often capture kernel oops that are not written to persistent storage.

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Exploitation scenarios and risk analysis​

This vulnerability is not an elevated-privilege remote exploit — but that does not make it low risk. Key exploitation scenarios:

• Local user causes repeated system crashes by manipulating display bindings (e.g., trigger module re-probe or expose a particular hardware state), affecting multi-user systems or multi-tenant devices.
• An attacker with some local interaction capability (for example, via a compromised unprivileged process) could create repeated availability loss as a denial-of-service attack.
• For appliances or IoT devices that accept display connections or have hot-pluggable displays, an untrusted external actor might cause device misconfiguration to trip the vulnerable path.

Constraints on attackers:

• Requires either physical or local access or the ability to cause driver re-probe operations.
• No evidence suggests the bug allows code execution or privilege escalation; it is an availability-focused issue.

Net risk: medium-to-high for environments where local access is possible (shared workstations, multi-user appliances, kiosks, embedded gateways). For single-user laptops, risk is lower unless local adversary access is plausible.

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Mitigation and remediation guidance​

Immediate priorities for administrators, integrators, and device vendors:

• Patch: apply kernel updates that include the VOP2 check fix. Keep platforms up to date with vendor kernel packages or stable kernel backports where available.
• For distributions: update to the kernel package version that includes the committed change in drivers/gpu/drm/rockchip/rockchip_drm_vop2.c; install available distribution security updates as soon as they are published.
• For embedded vendors and firmware integrators: rebuild device firmware/kernels including the patched commit and push OTA firmware updates to devices. Because many embedded products ship vendor kernels, this step is critical for remediation outside desktop/server distributions.

Practical steps for administrators and integrators:

• Identify affected systems:
• On each system, run uname -r to get the running kernel version.
• Check whether the rockchip VOP2 driver is present: grep the kernel config (zcat /proc/config.gz | grep ROCKCHIP) or check dmesg for rockchip DRM messages.
• Upgrade kernels:
• For general-purpose distributions, use the system package manager to apply security updates (apt, yum, zypper, dnf, etc..
• For systems with custom kernels, apply the patch or cherry-pick the commit into your kernel tree and rebuild.
• Backporting the patch:
• If maintaining a stable or long-term kernel branch, cherry-pick the upstream commit into your branch and run a full build and validation cycle. The patch is small and safe, but confirm via testing on representative hardware.
• Example backport workflow:
• git fetch origin refs/heads/master
• git checkout -b stable-fix-2025-38597 vX.Y.Z (your stable branch)
• git cherry-pick f9f68bf1d0efeadb6c427c9dbb30f307a7def19b
• make -j ... && run hardware smoke tests
• Temporary workarounds (only if immediate patching is impossible):
• Restrict unprivileged users from triggering driver probe operations (module reloads) by restricting access to /dev/dri and module manipulation.
• Disable the rockchip VOP2 driver as a kernel module at boot (blacklist) where hardware allows another display path and the feature is not required. Note: blacklisting will remove display support for affected video ports and is disruptive.
• For appliances, consider removing physical access to display ports or blocking non-admin hotplug events until firmware can be updated.

Testing and validation:

• After applying a patch or backport, validate display functionality across ports and confirm no kernel oops occurs during hot-plug or probe.
• Run regression tests specific to display paths and CRTC initialization sequences.

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Recommendations for stakeholders​

For system administrators​

• Prioritize updates for systems that are public-facing, multi-user, or that might be accessed by untrusted local users.
• Monitor kernel logs for DRM/rockchip errors and configure log retention to capture kernel oops.
• Coordinate with device vendors to confirm whether shipped devices are patched, and delay deployment of affected devices in sensitive environments until firmware updates are available.

For embedded device vendors and integrators​

• Rebuild and test vendor kernels with the patch included, and push firmware updates to devices on a schedule coordinated with customers.
• Provide clear advisories to customers explaining the impact (denial of display or device crash) and the steps to remediate (firmware update).
• Adopt a policy of upstreaming fixes and tracking stable kernel updates for security-relevant DRM and SoC driver code, to accelerate downstream remediation.

For distribution maintainers​

• Backport the minimal patch to relevant stable kernel branches and ship security updates with CVE references and changelog descriptions that make the effect and remediation clear.
• If the driver is not used on some architectures, document the risk and provide per-arch package status.

For security teams and incident responders​

• Treat occurrences of this driver-induced kernel crash as potential denial-of-service incidents. Correlate with user activity to determine whether crashes were accidental or induced.
• Use crash dumps and kernel oops logs to track affected host populations and to prioritize patching.

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Hardening and software engineering lessons​

This vulnerability is a textbook example of how assumptions about hardware invariants can lead to kernel-level instability. Key defensive lessons:

• Always validate pointers and preconditions before calling kernel APIs that assume the presence of resources. Defensive checks at probe time are cheap and often prevent severe failures.
• Hardware is messy: boards and SoCs can have legitimate configurations that violate typical assumptions made by drivers. Maintain test coverage across hardware permutations, especially for SoC drivers that run across many board designs.
• Small patches that add explicit failure modes (probe failure with clear logs) are preferable to allowing the code to proceed and trigger a kernel oops later.
• For security triage, availability-only bugs still merit high-priority fixes in distributed environments because denial-of-service can have direct operational impact.

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What cannot be proven (caveats)​

• There is no public evidence that CVE-2025-38597 has been used in targeted attacks for escalation or data theft; available information only documents the crash condition and the subsequent fix.
• The real-world exploitability depends on whether an attacker can produce the driver probe state remotely or locally: many scenarios require local access or vendor-specific interactions.
• Because vendor kernels and embedded firmware vary widely, the exact set of devices exposed and timelines for firmware updates are device-vendor dependent. Device owners should confirm patch availability with their vendor.

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Action checklist (concise, actionable)​

• Inventory: identify devices running Rockchip-based kernels (grep for rockchip in dmesg and kernel config).
• Log review: search kernel logs for vop2/drm/rockchip oops messages.
• Patch: apply vendor/distribution kernel updates that include the VOP2 fix or backport the commit into your kernel branch and deploy.
• Test: validate display behavior and run hardware regression tests.
• Mitigate temporarily: restrict module reloads and access to /dev/dri where feasible; consider driver blacklisting only as a last resort.
• Notify: inform affected stakeholders and users, especially for embedded devices that require firmware updates.

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Conclusion​

CVE-2025-38597 reinforces a perennial security and quality lesson: small assumptions in kernel drivers can produce high-impact availability faults when confronted with real-world hardware permutations. The fix is straightforward and conservative — fail probing cleanly when a required resource is absent — and it has been committed to the kernel and propagated through vendor advisories. The immediate priorities for operators are to identify affected systems, apply the fixed kernel packages or backport the commit into vendor kernels, and monitor for kernel oopses tied to the Rockchip VOP2 driver. Although this vulnerability does not enable data theft or privilege escalation, its ability to reliably take systems or devices offline makes timely patching essential for stable operations.

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Source: MSRC Security Update Guide - Microsoft Security Response Center