CVE-2026-68266
In the Linux kernel, the following vulnerability has been resolved:
drm/xe: Hold a dma-buf reference for imported BOs
An imported dma-buf BO is created as a ttm_bo_type_sg BO whose
reservation object is the exporter's dma_buf->resv. The importer,
however, only takes a dma-buf reference after a successful
dma_buf_dynamic_attach(). Until then nothing keeps the exporter alive,
so if the exporter is freed while the BO still references its resv, a
later access to that resv is a use-after-free:
Oops: general protection fault, probably for non-canonical address
0x6b6b6b6b6b6b6b9c
Workqueue: ttm ttm_bo_delayed_delete [ttm]
RIP: 0010:mutex_can_spin_on_owner+0x3f/0xc0
This can be reached on two paths:
- dma_buf_dynamic_attach() fails, or
- ttm_bo_init_reserved() fails during BO creation.
In both cases the BO already has bo->base.resv pointing at the exporter
resv, and sg BOs are always torn down via ttm_bo_delayed_delete(), which
locks bo->base.resv asynchronously - potentially after the exporter has
been freed.
Take the dma-buf reference in xe_bo_init_locked(), before
ttm_bo_init_reserved(), so it also covers a creation failure there, and
release it in xe_ttm_bo_destroy(). The reference is held for the whole
BO lifetime, keeping the shared resv alive on every path.
v2:
- Reworked the fix to avoid creating the imported sg BO before
dma_buf_dynamic_attach() succeeds.
- Attach with importer_priv == NULL and make invalidate_mappings ignore
incomplete imports.
v3:
- Dropped the xe-side reordering approach since importer_priv must be
valid when dma_buf_dynamic_attach() publishes the attachment.
- Per Christian's suggestion on the v1 thread, keyed the check on
import_attach rather than removing the sg guard entirely.
- Fixes both xe and amdgpu in a single TTM patch.
v4:
- Moved import_attach check to after dma_resv_copy_fences() so fences
are copied before returning for successful imports (Thomas).
- Removed exporter-alive
CSIRTS triage
- What
- Multiple vulnerabilities in the Linux kernel that may result in privilege escalation, denial of service, or information disclosure.
- Who is affected
- Debian systems running vulnerable Linux kernel versions.
- Urgency
- Multiple kernel vulnerabilities enabling privilege escalation and information leaks require urgent patching to protect system and data security.
- Action
- Apply the Debian security update DSA-6466-1 to the Linux kernel immediately.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.
Advisory coverage (2)
- unknownDSA-6466-1 linux - security updatedebian · 2026-08-25
- highCVE-2026-68266: In the Linux kernel, the following vulnerability has been resolved: drm/xe: Hold a dma-buf ref…nvd · 2026-08-10
External references
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