Bug 2535162 (CVE-2026-89801)

Summary: CVE-2026-89801 kernel: drm/nouveau/uvmm: fix premature region free on failed OP_UNMAP_SPARSE
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `drm/nouveau/uvmm` component. A local attacker could exploit a use-after-free vulnerability by triggering a premature region free during a failed `OP_UNMAP_SPARSE` operation. This occurs because certain failure paths do not properly clear a region pointer, leading to the system attempting to free a region that is still in use by another process. Successful exploitation could lead to system instability or potentially privilege escalation.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-16 11:04:33 UTC 
In the Linux kernel, the following vulnerability has been resolved:

drm/nouveau/uvmm: fix premature region free on failed OP_UNMAP_SPARSE

In nouveau_uvmm_bind_job_submit()'s OP_UNMAP_SPARSE arm, op->reg is set
from nouveau_uvma_region_find(), which only looks the region up and takes
no reference; a region's sole reference is its membership in
uvmm->region_mt. Two failure paths leave op->reg set: the -ENOENT check
when the region is busy, and the drm_gpuvm_sm_unmap_ops_create() failure.
The sibling nouveau_uvmm_sm_unmap_prepare() failure just below clears
op->reg; these two do not.

unwind_continue steps back one op, so the failing op is skipped by the
unwind loop and its op->reg stays set. nouveau_uvmm_bind_job_cleanup()
then enters its if (op->reg) branch and calls nouveau_uvma_region_remove()
and nouveau_uvma_region_put() on it, dropping the tree's sole reference
and freeing a region this job never created. The comment above the
cleanup loop documents the broken invariant: op->reg must be NULL on
submit failure.

This frees a live region on an unrelated failure, reachable single-job
when drm_gpuvm_sm_unmap_ops_create() returns -ENOMEM; if another job owns
the same region, its cleanup then removes and puts the freed region, a
use-after-free. Clear op->reg on both failure paths.
Comment 1 Mauro Matteo Cascella 2026-09-21 13:49:04 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89801.mbox