From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68437][MODERATE REGULAR] drm/imagination: Fit paired fragment job in the correct CCCB Date: Tue, 11 Aug 2026 21:06:08 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68437 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 15a9863929206911a08b6f62de9c5da6931dbc9e List-Id: CVE: CVE-2026-68437 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/imagination: Fit paired fragment job in the correct CCCB Commit: 15a9863929206911a08b6f62de9c5da6931dbc9e Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=15a9863929206911a08b6f62de9c5da6931dbc9e Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68437 Analysis date: Tue, 11 Aug 2026 21:06:08 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A local user with access to the affected PowerVR DRM device may trigger incorrect CCCB space accounting for paired fragment jobs, causing incomplete command submission, kernel warnings, and GPU job timeouts without evidence of memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68437 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68437 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: MODERATE REGULAR Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-68437 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-754;CWE-670;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A logic error in the PowerVR drm/imagination scheduler path can check CCCB space for a paired fragment job against the wrong queue. A local user able to submit GPU jobs through the DRM interface may cause prepare_job to believe that enough CCCB space is available, while run_job later cannot write the full command sequence. This can trigger kernel warnings and GPU job timeouts, resulting in denial of service for the affected GPU workload or graphics stack. For the CVSS the PR:L is used for the paranoid score because reliable triggering requires local code execution with access to the DRM device or render node, but does not necessarily require full administrative privileges. The issue is not network reachable. No confidentiality or integrity impact is assigned because the patch context indicates an incorrect queue and resource accounting problem rather than a proven UAF, OOB write, or arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-68437 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE LOCK INIT HARDWARE LINUS MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline / manual review recommended**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local user with access to the DRM render node may be able to submit paired geometry and fragment jobs. * Availability impact realistic: +1. The described failure can cause kernel warnings and GPU job timeouts, affecting the graphics or GPU workload. Paranoid additional signal: * Reliable strong DoS concern: +1. If the timeout path repeatedly wedges the GPU scheduler or affects graphics recovery, this can be treated as a stronger local DoS. Signals not applied: * No generic memory corruption. The patch shows wrong CCCB queue selection and incorrect resource accounting, not UAF, OOB write, double free, type confusion, or arbitrary write. * No privilege escalation plausible signal. There is no demonstrated reclaim, object replacement, callback control, refcount abuse, or write primitive. * No confidentiality or integrity impact. The bug affects scheduling and command submission completeness, not data disclosure or unauthorized modification. * No remote reachability. The path is local DRM job submission, not network-facing. * No high-control API bonus. GPU ioctls alone are not enough under the provided rule without evidence of exploitation-relevant memory layout, lifetime, callback, refcount, DMA mapping, or page ownership control. ## 3. Reachability analysis The likely trigger is a local process that can submit jobs to the affected PowerVR DRM driver, commonly through a render node if exposed by system policy. Root is not inherently required, so PR:L is the practical paranoid interpretation. Namespaces and containers may matter if the DRM device node is passed through to a container. Without device access, the bug is not reachable from an ordinary confined container. The affected path is hardware and driver specific. It requires an Imagination PowerVR DRM environment and paired geometry and fragment job submission. It is not a broad default kernel path and is not remotely reachable. Call-site confidence: high. The patch includes the relevant prepare_job path and the paired fragment dependency handling. ## 4. Severity interpretation This behaves like an ordinary Moderate or borderline local DoS, not an Important-class kernel vulnerability. The realistic impact is GPU job timeout or graphics stack disruption. The theoretical concern is limited because the patch does not show memory corruption, stale lifetime use, attacker-controlled overwrite, or cross-object corruption. The paranoid score reaches 3 only because local unprivileged DRM access plus potentially repeatable GPU timeout may justify manual review. It does not reach Actionable Moderate or Important under the given formula. ## 5. One-sentence report phrase A local user with access to the affected PowerVR DRM device may trigger incorrect CCCB space accounting for paired fragment jobs, causing incomplete command submission, kernel warnings, and GPU job timeouts without evidence of memory corruption or privilege escalation. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED This is not a strong security candidate, but the GPU scheduler timeout behavior and local render node reachability justify a lightweight manual check before auto-closing. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/imagination: Fit paired fragment job in the correct CCCB Commit: 15a9863929206911a08b6f62de9c5da6931dbc9e Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=15a9863929206911a08b6f62de9c5da6931dbc9e Commit description: For geometry jobs with a paired fragment job, at the moment, the DRM scheduler's prepare_job() callback: - checks for internal (driver) dependencies for the geometry job; - calls into pvr_queue_get_paired_frag_job_dep() to check for external dependencies for the fragment job (the two jobs are submitted together but the common scheduler code doesn't know about it, so this needs to be done at this point in time); - calls into the prepare_job() callback again, but for the fragment job, to check its internal dependencies as well, passing the fragment job's drm_sched_job and the geometry job's drm_sched_entity / pvr_queue. The problem with the last step is that pvr_queue_prepare_job() doesn't always take the mismatched fragment job and geometry queue into account, in particular when checking whether there is space for the fragment command to be submitted, so the code ends up checking for space in the geometry (i.e. wrong) CCCB. The rest of the nested prepare_job() callback happens to work fine at the moment as the other internal dependencies are not relevant for a paired fragment job. Move the initialisation of a paired fragment job's done fence and CCCB fence to pvr_queue_get_paired_frag_job_dep(), inferring the correct queue from the fragment job itself. This fixes cases where prepare_job() wrongly assumed that there was enough space for a paired fragment job in its own CCCB, 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): [ 552.421075] WARNING: drivers/gpu/drm/imagination/pvr_cccb.c:178 at pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr], CPU#2: kworker/u16:5/63 [ 552.421230] Modules linked in: [ 552.421592] CPU: 2 UID: 0 PID: 63 Comm: kworker/u16:5 Tainted: G W 7.0.0-rc2-gc5d053e4dccb #39 PREEMPT [ 552.421625] Tainted: [W]=WARN [ 552.421637] Hardware name: Texas Instruments AM625 SK (DT) [ 552.421655] Workqueue: powervr-sched drm_sched_run_job_work [gpu_sched] [ 552.421744] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 552.421766] pc : pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] [ 552.421850] lr : pvr_queue_submit_job_to_cccb+0x57c/0xa74 [powervr] [ 552.421923] sp : ffff800084c47650 [ 552.421936] x29: ffff800084c47740 x28: 0000000000000df8 x27: ffff800088a77000 [ 552.421979] x26: 0000000000000030 x25: ffff800084c47680 x24: 0000000000001000 [ 552.422017] x23: ffff800084c47820 x22: 1ffff00010988ecc x21: 0000000000000008 [ 552.422055] x20: 0000000000000208 x19: ffff000006ad5a88 x18: 0000000000000000 [ 552.422093] x17: 0000000020020000 x16: 0000000000020000 x15: 0000000000000000 [ 552.422130] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 [ 552.422167] x11: 000000000000f2f2 x10: 00000000f3000000 x9 : 00000000f3f3f3f3 [ 552.422204] x8 : 00000000f2f2f200 x7 : ffff700010988ecc x6 : 0000000000000008 [ 552.422241] x5 : 0000000000000000 x4 : 1ffff0001114ee00 x3 : 0000000000000000 [ 552.422278] x2 : 0000000000000007 x1 : 0000000000000fff x0 : 000000000000002f [ 552.422316] Call trace: [ 552.422330] pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] (P) [ 552.422411] pvr_queue_submit_job_to_cccb+0x57c/0xa74 [powervr] [ 552.422486] pvr_queue_run_job+0x3a4/0x990 [powervr] [ 552.422562] drm_sched_run_job_work+0x580/0xd48 [gpu_sched] [ 552.422623] process_one_work+0x520/0x1288 [ 552.422657] worker_thread+0x3f0/0xb3c [ 552.422679] kthread+0x334/0x3d8 [ 552.422706] ret_from_fork+0x10/0x20 Fixes: eaf01ee ("drm/imagination: Implement job submission and scheduling") Cc: stable@vger.kernel.org Signed-off-by: Alessio Belle Reviewed-by: Brajesh Gupta Link: https://patch.msgid.link/20260330-job-submission-fixes-cleanup-v1-2-7de8c09cef8c@imgtec.com Signed-off-by: Matt Coster Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/imagination/pvr_cccb.c drivers/gpu/drm/imagination/pvr_queue.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=15a9863929206911a08b6f62de9c5da6931dbc9e ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68437 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68437 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: 2 Paranoid ActionableScore: 3 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE REGULAR These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).