Description
In the Linux kernel, the following vulnerability has been resolved:

drm/imagination: Count paired job fence as dependency in prepare_job()

The DRM scheduler's prepare_job() callback counts the remaining
non-signaled native dependencies for a job, preventing job submission
until those (plus job data and fence update) can fit in the job queue's
CCCB.

This means checking which dependencies can be waited upon in the
firmware, i.e. whether they are backed by a UFO object, i.e. whether
their drm_sched_fence::parent has been assigned to a
pvr_queue_fence::base fence. That happens when the job owning the fence
is submitted to the firmware.

Paired geometry and fragment jobs are submitted at the same time, which
means the dependency between them can't be checked this way before
submission.

Update job_count_remaining_native_deps() to take into account the
dependency between paired jobs.

This fixes cases where prepare_job() underestimated the space left in
an almost full fragment CCCB, wrongly unblocking run_job(), which then
returned early without writing the full sequence of commands to the
CCCB.

The above lead to kernel warnings such as the following and potentially
job timeouts (depending on waiters on the missing commands):

[ 375.702979] WARNING: drivers/gpu/drm/imagination/pvr_cccb.c:178 at pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr], CPU#1: kworker/u16:3/47
[ 375.703160] Modules linked in:
[ 375.703571] CPU: 1 UID: 0 PID: 47 Comm: kworker/u16:3 Tainted: G W 7.0.0-rc2-g817eb6b11ad5 #40 PREEMPT
[ 375.703613] Tainted: [W]=WARN
[ 375.703627] Hardware name: Texas Instruments AM625 SK (DT)
[ 375.703645] Workqueue: powervr-sched drm_sched_run_job_work [gpu_sched]
[ 375.703741] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 375.703764] pc : pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr]
[ 375.703847] lr : pvr_queue_submit_job_to_cccb+0x578/0xa70 [powervr]
[ 375.703921] sp : ffff800084a97650
[ 375.703934] x29: ffff800084a97740 x28: 0000000000000958 x27: ffff80008565d000
[ 375.703979] x26: 0000000000000030 x25: ffff800084a97680 x24: 0000000000001000
[ 375.704017] x23: ffff800084a97820 x22: 1ffff00010952ecc x21: 0000000000000008
[ 375.704056] x20: 00000000000006a8 x19: ffff00002ff7da88 x18: 0000000000000000
[ 375.704093] x17: 0000000020020000 x16: 0000000000020000 x15: 0000000000000000
[ 375.704132] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
[ 375.704168] x11: 000000000000f2f2 x10: 00000000f3000000 x9 : 00000000f3f3f3f3
[ 375.704206] x8 : 00000000f2f2f200 x7 : ffff700010952ecc x6 : 0000000000000008
[ 375.704243] x5 : 0000000000000000 x4 : 1ffff00010acba00 x3 : 0000000000000000
[ 375.704279] x2 : 0000000000000007 x1 : 0000000000000fff x0 : 000000000000002f
[ 375.704317] Call trace:
[ 375.704331] pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] (P)
[ 375.704411] pvr_queue_submit_job_to_cccb+0x578/0xa70 [powervr]
[ 375.704487] pvr_queue_run_job+0x3a4/0x990 [powervr]
[ 375.704562] drm_sched_run_job_work+0x580/0xd48 [gpu_sched]
[ 375.704623] process_one_work+0x520/0x1288
[ 375.704658] worker_thread+0x3f0/0xb3c
[ 375.704680] kthread+0x334/0x3d8
[ 375.704706] ret_from_fork+0x10/0x20
[ 375.704736] ---[ end trace 0000000000000000 ]---
Published: 2026-08-10
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

A logic error in the DRM scheduler’s prepare_job() callback causes the kernel to undercount native dependencies for paired job fences, leading to premature unblocking of job execution and incomplete command writes to the command completion control block (CCCB). This can result in kernel warnings, job timeouts, and unreliable GPU operations, effectively denying service to applications relying on GPU acceleration.

Affected Systems

The vulnerability affects the Linux kernel's DRM/powervr subsystems on all Linux platforms. No specific kernel version is listed, but the bug was addressed in a commit referenced in the provided kernel links. Users running kernels that still include the buggy drm/imagination scheduler logic are impacted.

Risk and Exploitability

The CVSS score is not disclosed, but the EPSS score is unavailable and the vulnerability is not listed in CISA KEV. The likely attack vector is a local attacker with kernel privileges or an exploit that causes the kernel to schedule paired geometry and fragment jobs in an almost full CCCB. The exploit could lead to kernel warnings and a denial of GPU service, potentially causing system instability without granting arbitrary code execution.

Generated by OpenCVE AI on August 10, 2026 at 15:25 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade the Linux kernel to a version that includes the drm/imagination scheduler fix referenced in the provided kernel commits
  • Apply any vendor‐issued firmware or driver updates for the PowerVR (Powervr) GPU driver that may mitigate the CCCB write issue
  • Monitor system logs for kernel warnings related to pvr_cccb_write_command_with_header and verify that the issue no longer occurs after the patch

Generated by OpenCVE AI on August 10, 2026 at 15:25 UTC.

Tracking

Sign in to view the affected projects.

Advisories

No advisories yet.

History

Mon, 10 Aug 2026 12:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: drm/imagination: Count paired job fence as dependency in prepare_job() The DRM scheduler's prepare_job() callback counts the remaining non-signaled native dependencies for a job, preventing job submission until those (plus job data and fence update) can fit in the job queue's CCCB. This means checking which dependencies can be waited upon in the firmware, i.e. whether they are backed by a UFO object, i.e. whether their drm_sched_fence::parent has been assigned to a pvr_queue_fence::base fence. That happens when the job owning the fence is submitted to the firmware. Paired geometry and fragment jobs are submitted at the same time, which means the dependency between them can't be checked this way before submission. Update job_count_remaining_native_deps() to take into account the dependency between paired jobs. This fixes cases where prepare_job() underestimated the space left in an almost full fragment CCCB, wrongly unblocking run_job(), which then returned early without writing the full sequence of commands to the CCCB. The above lead to kernel warnings such as the following and potentially job timeouts (depending on waiters on the missing commands): [ 375.702979] WARNING: drivers/gpu/drm/imagination/pvr_cccb.c:178 at pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr], CPU#1: kworker/u16:3/47 [ 375.703160] Modules linked in: [ 375.703571] CPU: 1 UID: 0 PID: 47 Comm: kworker/u16:3 Tainted: G W 7.0.0-rc2-g817eb6b11ad5 #40 PREEMPT [ 375.703613] Tainted: [W]=WARN [ 375.703627] Hardware name: Texas Instruments AM625 SK (DT) [ 375.703645] Workqueue: powervr-sched drm_sched_run_job_work [gpu_sched] [ 375.703741] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 375.703764] pc : pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] [ 375.703847] lr : pvr_queue_submit_job_to_cccb+0x578/0xa70 [powervr] [ 375.703921] sp : ffff800084a97650 [ 375.703934] x29: ffff800084a97740 x28: 0000000000000958 x27: ffff80008565d000 [ 375.703979] x26: 0000000000000030 x25: ffff800084a97680 x24: 0000000000001000 [ 375.704017] x23: ffff800084a97820 x22: 1ffff00010952ecc x21: 0000000000000008 [ 375.704056] x20: 00000000000006a8 x19: ffff00002ff7da88 x18: 0000000000000000 [ 375.704093] x17: 0000000020020000 x16: 0000000000020000 x15: 0000000000000000 [ 375.704132] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 [ 375.704168] x11: 000000000000f2f2 x10: 00000000f3000000 x9 : 00000000f3f3f3f3 [ 375.704206] x8 : 00000000f2f2f200 x7 : ffff700010952ecc x6 : 0000000000000008 [ 375.704243] x5 : 0000000000000000 x4 : 1ffff00010acba00 x3 : 0000000000000000 [ 375.704279] x2 : 0000000000000007 x1 : 0000000000000fff x0 : 000000000000002f [ 375.704317] Call trace: [ 375.704331] pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] (P) [ 375.704411] pvr_queue_submit_job_to_cccb+0x578/0xa70 [powervr] [ 375.704487] pvr_queue_run_job+0x3a4/0x990 [powervr] [ 375.704562] drm_sched_run_job_work+0x580/0xd48 [gpu_sched] [ 375.704623] process_one_work+0x520/0x1288 [ 375.704658] worker_thread+0x3f0/0xb3c [ 375.704680] kthread+0x334/0x3d8 [ 375.704706] ret_from_fork+0x10/0x20 [ 375.704736] ---[ end trace 0000000000000000 ]---
Title drm/imagination: Count paired job fence as dependency in prepare_job()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-10T12:02:13.103Z

Reserved: 2026-07-30T09:28:09.379Z

Link: CVE-2026-68281

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-10T20:15:03Z

Weaknesses

No weakness.