drm/drm_exec: fix up contended obj when num_objects is 0
drm_exec_prepare_array() silently returns success without calling
drm_exec_lock_contended() when num_objects is zero. This breaks the
invariant upheld by drm_exec_lock_obj(), where every entry point into
the locking sequence must first attempt to lock any previously
contended object before proceeding.
Drivers that chain multiple drm_exec_prepare_array() calls per
drm_exec_until_all_locked() iteration (e.g. amdgpu's userq signal/wait
ioctls, which prepare separate read and write BO arrays) can pass an
empty array for one of the two calls. If contention is hit while
preparing the non-empty array, exec->contended is set and the loop
retries; on retry, the empty-array call preceding it is a no-op that
never clears exec->contended, so drm_exec_retry_on_contention()
immediately jumps back to the top of the loop without ever reaching
the call that would resolve the contention. This spins forever.
Fix it by having drm_exec_prepare_array() call drm_exec_lock_contended()
directly when num_objects is zero, so a pending contended object dont
loop infinitely.
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No vendor fix or workaround currently provided.
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Fri, 25 Sep 2026 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: drm/drm_exec: fix up contended obj when num_objects is 0 drm_exec_prepare_array() silently returns success without calling drm_exec_lock_contended() when num_objects is zero. This breaks the invariant upheld by drm_exec_lock_obj(), where every entry point into the locking sequence must first attempt to lock any previously contended object before proceeding. Drivers that chain multiple drm_exec_prepare_array() calls per drm_exec_until_all_locked() iteration (e.g. amdgpu's userq signal/wait ioctls, which prepare separate read and write BO arrays) can pass an empty array for one of the two calls. If contention is hit while preparing the non-empty array, exec->contended is set and the loop retries; on retry, the empty-array call preceding it is a no-op that never clears exec->contended, so drm_exec_retry_on_contention() immediately jumps back to the top of the loop without ever reaching the call that would resolve the contention. This spins forever. Fix it by having drm_exec_prepare_array() call drm_exec_lock_contended() directly when num_objects is zero, so a pending contended object dont loop infinitely. | |
| Title | drm/drm_exec: fix up contended obj when num_objects is 0 | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:22:28.057Z
Reserved: 2026-09-25T10:18:58.200Z
Link: CVE-2026-97900
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:16.787
Modified: 2026-09-25T11:17:16.787
Link: CVE-2026-97900
Redhat
No data.
OpenCVE Enrichment
No data.
No weakness.