From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64184][LOW] mm/damon/sysfs-schemes: call missing mem_cgroup_iter_break() Date: Sun, 19 Jul 2026 15:53:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64184 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: 082351f9d40007414ad6af062b3a26fa02fd4b5f List-Id: CVE: CVE-2026-64184 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: mm/damon/sysfs-schemes: call missing mem_cgroup_iter_break() Commit: 082351f9d40007414ad6af062b3a26fa02fd4b5f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=082351f9d40007414ad6af062b3a26fa02fd4b5f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64184 Analysis date: Sun, 19 Jul 2026 15:53:07 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A missing `mem_cgroup_iter_break()` in the DAMON sysfs memcg lookup path can leak cgroup references during privileged DAMON scheme configuration, potentially causing resource exhaustion after repeated operations but not memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64184 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64184 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: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-64184 LOW 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:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-404;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'damon_sysfs_memcg_path_to_id can leak a cgroup reference when it finds a matching memory cgroup and exits the mem_cgroup_iter loop without calling mem_cgroup_iter_break(). The bug is a resource reference leak rather than memory corruption. For the CVSS the PR:H is used because DAMON sysfs scheme configuration is normally restricted to root or CAP_SYS_ADMIN. The issue is not network reachable and requires local control of the DAMON sysfs configuration path. Impact is denial of service through possible resource exhaustion after repeated operations, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES SIMPLEFIX LEAK LINUS MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like** ## 2. Signal breakdown * Availability impact realistic: +1 paranoid only. Repeated DAMON sysfs operations could theoretically accumulate leaked cgroup references and contribute to resource exhaustion. * Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. DAMON sysfs scheme configuration is normally an administrative interface. * Rare or non-default subsystem exposure: -1. DAMON sysfs scheme filters are not a broadly exposed default attack surface. * No memory corruption signal: +0. The patch fixes a missing `mem_cgroup_iter_break()` and describes a reference leak, not UAF, double free, OOB access, type confusion, or arbitrary write. * No confidentiality or integrity signal: +0. There is no demonstrated readback, sensitive-object access, permission bypass, or writable corruption primitive. ## 3. Reachability analysis The bug is reachable through local DAMON sysfs configuration paths, specifically when resolving a memcg path in `damon_sysfs_memcg_path_to_id()`. In typical deployments this requires root or CAP_SYS_ADMIN-like control over DAMON configuration. It is not network reachable. Containers or delegated environments could matter only if DAMON sysfs control is exposed to a reduced-privilege actor, which is uncommon and should be treated as environment-specific. ## 4. Severity interpretation This behaves like a low-priority resource leak rather than an actionable memory corruption issue. The theoretical worst case is resource exhaustion after repeated privileged operations, but the patch does not support privilege escalation, sensitive data exposure, object reuse, UAF, or cross-boundary bypass. It should not be treated as Important-class. ## 5. One-sentence report phrase A missing `mem_cgroup_iter_break()` in the DAMON sysfs memcg lookup path can leak cgroup references during privileged DAMON scheme configuration, potentially causing resource exhaustion after repeated operations but not memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This is a privileged local resource reference leak with no concrete memory corruption or security-boundary bypass primitive, so it can be handled as ordinary Low/Moderate maintenance unless the product exposes DAMON sysfs controls to untrusted users. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mm/damon/sysfs-schemes: call missing mem_cgroup_iter_break() Commit: 082351f9d40007414ad6af062b3a26fa02fd4b5f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=082351f9d40007414ad6af062b3a26fa02fd4b5f Commit description: damon_sysfs_memcg_path_to_id() breaks mem_cgroup_iter() loop without calling mem_cgroup_iter_break(). This leaks the cgroup reference. Fix the issue by calling mem_cgroup_iter_break() before the break. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260426173625.86521-1-sj@kernel.org Link: https://lore.kernel.org/20260423004148.74722-1-sj@kernel.org [1] Fixes: 29cbb9a ("mm/damon/sysfs-schemes: implement scheme filters") Signed-off-by: SeongJae Park Cc: # 6.3.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman Changed files: mm/damon/sysfs-schemes.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=082351f9d40007414ad6af062b3a26fa02fd4b5f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64184 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64184 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:L/PR:H/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.4 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: 0 Paranoid ActionableScore: 1 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).