# CVE-2024-26939: drm/i915/vma: Fix UAF on destroy against retire race > A race condition in the Intel i915 GPU driver allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges. - **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 1 May 2024 - **Updated:** 5 Aug 2026 - **Also known as:** BELL-CVE-2024-26939, DEBIAN-CVE-2024-26939, GHSA-gghh-gpx3-pmx6, UBUNTU-CVE-2024-26939 ## What is CVE-2024-26939? CVE-2024-26939 is a high-severity use after free vulnerability in Linux kernel, published on 1 May 2024. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description In the Linux kernel, the following vulnerability has been resolved: drm/i915/vma: Fix UAF on destroy against retire race Object debugging tools were sporadically reporting illegal attempts to free a still active i915 VMA object when parking a GT believed to be idle. [161.359441] ODEBUG: free active (active state 0) object: ffff88811643b958 object type: i915_active hint: __i915_vma_active+0x0/0x50 [i915] [161.360082] WARNING: CPU: 5 PID: 276 at lib/debugobjects.c:514 debug_print_object+0x80/0xb0 ... [161.360304] CPU: 5 PID: 276 Comm: kworker/5:2 Not tainted 6.5.0-rc1-CI_DRM_13375-g003f860e5577+ #1 [161.360314] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022 [161.360322] Workqueue: i915-unordered __intel_wakeref_put_work [i915] [161.360592] RIP: 0010:debug_print_object+0x80/0xb0 ... [161.361347] debug_object_free+0xeb/0x110 [161.361362] i915_active_fini+0x14/0x130 [i915] [161.361866] release_references+0xfe/0x1f0 [i915] [161.362543] i915_vma_parked+0x1db/0x380 [i915] [161.363129] __gt_park+0x121/0x230 [i915] [161.363515] ____intel_wakeref_put_last+0x1f/0x70 [i915] That has been tracked down to be happening when another thread is deactivating the VMA inside __active_retire() helper, after the VMA's active counter has been already decremented to 0, but before deactivation of the VMA's object is reported to the object debugging tool. We could prevent from that race by serializing i915_active_fini() with __active_retire() via ref->tree_lock, but that wouldn't stop the VMA from being used, e.g. from __i915_vma_retire() called at the end of __active_retire(), after that VMA has been already freed by a concurrent i915_vma_destroy() on return from the i915_active_fini(). Then, we should rather fix the issue at the VMA level, not in i915_active. Since __i915_vma_parked() is called from __gt_park() on last put of the GT's wakeref, the issue could be addressed by holding the GT wakeref long enough for __active_retire() to complete before that wakeref is released and the GT parked. I believe the issue was introduced by commit d93939730347 ("drm/i915: Remove the vma refcount") which moved a call to i915_active_fini() from a dropped i915_vma_release(), called on last put of the removed VMA kref, to i915_vma_parked() processing path called on last put of a GT wakeref. However, its visibility to the object debugging tool was suppressed by a bug in i915_active that was fixed two weeks later with commit e92eb246feb9 ("drm/i915/active: Fix missing debug object activation"). A VMA associated with a request doesn't acquire a GT wakeref by itself. Instead, it depends on a wakeref held directly by the request's active intel_context for a GT associated with its VM, and indirectly on that intel_context's engine wakeref if the engine belongs to the same GT as the VMA's VM. Those wakerefs are released asynchronously to VMA deactivation. Fix the issue by getting a wakeref for the VMA's GT when activating it, and putting that wakeref only after the VMA is deactivated. However, exclude global GTT from that processing path, otherwise the GPU never goes idle. Since __i915_vma_retire() may be called from atomic contexts, use async variant of wakeref put. Also, to avoid circular locking dependency, take care of acquiring the wakeref before VM mutex when both are needed. v7: Add inline comments with justifications for: - using untracked variants of intel_gt_pm_get/put() (Nirmoy), - using async variant of _put(), - not getting the wakeref in case of a global GTT, - always getting the first wakeref outside vm->mutex. v6: Since __i915_vma_active/retire() callbacks are not serialized, storing a wakeref tracking handle inside struct i915_vma is not safe, and there is no other good place for that. Use untracked variants of intel_gt_pm_get/put_async(). v5: Replace "tile" with "GT" across commit description (Rodrigo), - ---truncated--- Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2024-26939? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2024-26939? Apply the vendor's patch. ## Is CVE-2024-26939 being exploited? There is no known exploitation of CVE-2024-26939 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2024-26939 and fix it if it is affected. What it is: CVE-2024-26939 is a high-severity use after free vulnerability in Linux kernel, published on 1 May 2024. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2024-26939 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2024-26939/ (Markdown: https://insights.sbomify.com/CVE-2024-26939/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2024-26939 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-26939 - OSV: https://osv.dev/vulnerability/CVE-2024-26939 --- From sbomify Insights: https://insights.sbomify.com/CVE-2024-26939/ Summaries are generated and may contain mistakes; the official description above is the record.