CVE-2025-40096
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-30

Last updated on: 2025-10-30

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: drm/sched: Fix potential double free in drm_sched_job_add_resv_dependencies When adding dependencies with drm_sched_job_add_dependency(), that function consumes the fence reference both on success and failure, so in the latter case the dma_fence_put() on the error path (xarray failed to expand) is a double free. Interestingly this bug appears to have been present ever since commit ebd5f74255b9 ("drm/sched: Add dependency tracking"), since the code back then looked like this: drm_sched_job_add_implicit_dependencies(): ... for (i = 0; i < fence_count; i++) { ret = drm_sched_job_add_dependency(job, fences[i]); if (ret) break; } for (; i < fence_count; i++) dma_fence_put(fences[i]); Which means for the failing 'i' the dma_fence_put was already a double free. Possibly there were no users at that time, or the test cases were insufficient to hit it. The bug was then only noticed and fixed after commit 9c2ba265352a ("drm/scheduler: use new iterator in drm_sched_job_add_implicit_dependencies v2") landed, with its fixup of commit 4eaf02d6076c ("drm/scheduler: fix drm_sched_job_add_implicit_dependencies"). At that point it was a slightly different flavour of a double free, which commit 963d0b356935 ("drm/scheduler: fix drm_sched_job_add_implicit_dependencies harder") noticed and attempted to fix. But it only moved the double free from happening inside the drm_sched_job_add_dependency(), when releasing the reference not yet obtained, to the caller, when releasing the reference already released by the former in the failure case. As such it is not easy to identify the right target for the fixes tag so lets keep it simple and just continue the chain. While fixing we also improve the comment and explain the reason for taking the reference and not dropping it.
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Meta Information
Published
2025-10-30
Last Modified
2025-10-30
Generated
2026-05-07
AI Q&A
2025-10-30
EPSS Evaluated
2026-05-05
NVD
CVE-2025-40096
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a double free bug in the Linux kernel's DRM scheduler code. Specifically, when adding dependencies using drm_sched_job_add_dependency(), the function incorrectly consumes a fence reference both on success and failure. On failure (such as when the xarray fails to expand), this leads to a double free of the dma_fence object. The bug has existed since the initial implementation of dependency tracking and was only noticed and fixed after subsequent commits. The issue involves improper reference counting and releasing of dma_fence objects, causing memory management errors.


How can this vulnerability impact me? :

This vulnerability can cause a double free in kernel memory management, which may lead to kernel crashes, instability, or potentially allow an attacker to execute arbitrary code or escalate privileges by exploiting the memory corruption.


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