CVE-2025-40096

Description

In the Linux kernel, the following vulnerability has been resolved:drm/sched: Fix potential double free in drm_sched_job_add_resv_dependenciesWhen adding dependencies with drm_sched_job_add_dependency(), thatfunction consumes the fence reference both on success and failure, so inthe latter case the dma_fence_put() on the error path (xarray failed toexpand) is a double free.Interestingly this bug appears to have been present ever sincecommit ebd5f74255b9 (drm/sched: Add dependency tracking), since the codeback 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 doublefree. Possibly there were no users at that time, or the test cases wereinsufficient to hit it.The bug was then only noticed and fixed aftercommit 9c2ba265352a (drm/scheduler: use new iterator in drm_sched_job_add_implicit_dependencies v2)landed, with its fixup ofcommit 4eaf02d6076c (drm/scheduler: fix drm_sched_job_add_implicit_dependencies).At that point it was a slightly different flavour of a double free, whichcommit 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 thedrm_sched_job_add_dependency(), when releasing the reference not yetobtained, to the caller, when releasing the reference already released bythe former in the failure case.As such it is not easy to identify the right target for the fixes tag solets keep it simple and just continue the chain.While fixing we also improve the comment and explain the reason for takingthe reference and not dropping it.

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234