From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74574][IMPORTANT] dmaengine: idxd: fix fdev setup failure cleanup in idxd_cdev_open() [ Upstream Date: Sat, 15 Aug 2026 16:55:47 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74574 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 6 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 778ccbded2c8749c5be7f0dfa04fc9977a36fb7e List-Id: CVE: CVE-2026-74574 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: dmaengine: idxd: fix fdev setup failure cleanup in idxd_cdev_open() [ Upstream Commit: 778ccbded2c8749c5be7f0dfa04fc9977a36fb7e Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=778ccbded2c8749c5be7f0dfa04fc9977a36fb7e Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74574 Analysis date: Sat, 15 Aug 2026 16:55:47 -0400 ActionableScore: 6 ActionableScore lower bound: 5 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A failed idxd file-device setup path can call `put_device(fdev)` while holding `wq_lock` and then continue into stale `ctx` cleanup, causing deadlock and possible UAF or double-free in a local DMA accelerator device path. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74574 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74574 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: IMPORTANT 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-2026-74574 IMPORTANT CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-415;*CWE-833;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'idxd_cdev_open() can hit an unsafe cleanup path when file device setup fails after the ctx and fdev objects were partially initialized. The failure path called put_device(fdev) while wq_lock was still held, so idxd_file_dev_release() could run synchronously and try to take the same lock again, causing a deadlock. The same path could then fall through into later ctx cleanup even though the release callback owns that cleanup, so idxd_xa_pasid_remove(ctx) and kfree(ctx) may operate on an already freed ctx. For the CVSS the PR:L is used because a local user or process needs permission to open the idxd character device, but full administrator privileges are not necessarily required in deployments that delegate accelerator access. The issue is not network reachable. Impact is at least a local denial of service via deadlock or kernel crash and in worst case may allow confidentiality or integrity impact due to use after free or double free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 7) YES LOCK DEADLOCK UAF HARDWARE KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: 5 * Paranoid score: 6 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 Opening the idxd character device may be available to non-root users in deployments that delegate accelerator workqueue access. * Memory corruption, strong corruption primitive: +2 The commit explicitly says the path may call `idxd_xa_pasid_remove(ctx)` and `kfree(ctx)` after `idxd_file_dev_release()` already owns and frees `ctx`, making this a UAF or double-free candidate. * Real lifetime corruption: +1 This is a concrete object lifetime bug involving `fdev`, release callbacks, `ctx` ownership, and cleanup ordering. * Reliable kernel crash / strong DoS: +1 The `put_device(fdev)` path can synchronously invoke the release callback while `wq_lock` is held, causing a deadlock. The later freed-ctx cleanup can also crash. * Privileged kernel/device-management memory corruption path: +1 The bug is in a DMA accelerator driver character-device open path and affects device/workqueue lifetime management. * Hard or unreliable failure condition: -1 Triggering requires the file-device setup path to fail after partial initialization, e.g. `dev_set_name()` or `device_add()` failure. * Corruption primitive constrained or not attacker-controlled: -1 The patch does not show attacker-controlled reclaim, controlled replacement, arbitrary write, callback hijack, or type confusion. Paranoid-only adjustment: * Weak LPE concern: +1 Because UAF/double-free on a driver context exists in a DMA/device-management path, privilege escalation cannot be excluded for triage, but no strong exploit primitive is demonstrated. ## 3. Reachability analysis The bug is local and is reached through `idxd_cdev_open()`. It is not network reachable. Typical reachability depends on whether Intel DSA/IDXD hardware is present, the driver is loaded, workqueues are configured, and the character device is exposed to the user. On many systems this is a specialized hardware path, but in accelerator-enabled deployments access may be delegated to non-root service users or container workloads. Full host root should not be assumed if the security model intentionally grants limited accelerator access. Call-site confidence: medium-high. The provided patch shows the failing open-path labels and the commit message explicitly describes the synchronous release callback and freed `ctx` cleanup consequence. ## 4. Severity interpretation This is stronger than an ordinary Moderate deadlock because the same failure path also creates a real lifetime-corruption condition on `ctx`. Realistic exploitation evidence supports local DoS and kernel crash/deadlock. Privilege escalation is plausible only in a paranoid triage sense because the patch indicates UAF/double-free, but it does not show attacker-controlled reclaim, object replacement, arbitrary write, or callback control. Therefore this should be treated as Actionable Moderate at minimum, not auto-closed. ## 5. One-sentence report phrase A failed idxd file-device setup path can call `put_device(fdev)` while holding `wq_lock` and then continue into stale `ctx` cleanup, causing deadlock and possible UAF or double-free in a local DMA accelerator device path. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch explicitly describes UAF/double-free behavior in addition to deadlock, and the affected path may be reachable by delegated non-root users on systems exposing idxd accelerator devices. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dmaengine: idxd: fix fdev setup failure cleanup in idxd_cdev_open() [ Upstream Commit: 778ccbded2c8749c5be7f0dfa04fc9977a36fb7e Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=778ccbded2c8749c5be7f0dfa04fc9977a36fb7e Changed files: drivers/dma/idxd/cdev.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=778ccbded2c8749c5be7f0dfa04fc9977a36fb7e ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74574 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74574 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: 5 Paranoid ActionableScore: 6 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).