From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64182][LOW] drivers/base/memory: fix memory block reference leak in poison accounting Date: Sun, 19 Jul 2026 15:44:30 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64182 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: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 686b4283f82cd630fafd7ca9b03dfc080b3ec8fa List-Id: CVE: CVE-2026-64182 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: drivers/base/memory: fix memory block reference leak in poison accounting Commit: 686b4283f82cd630fafd7ca9b03dfc080b3ec8fa Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=686b4283f82cd630fafd7ca9b03dfc080b3ec8fa Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64182 Analysis date: Sun, 19 Jul 2026 15:44:30 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A missing `put_device()` in memory block hwpoison accounting leaks `memory_block` device references on successful lookups, potentially causing local privileged resource leakage or hotplug cleanup issues but not memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64182 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64182 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-2026-64182 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-401;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'A reference leak in memory block poison accounting occurs because memblk_nr_poison_inc and memblk_nr_poison_sub call find_memory_block_by_id which takes a device reference, but the old code did not release it after updating nr_hwpoison. Repeated successful hwpoison accounting operations can pin memory_block device objects and may interfere with memory block teardown or hotplug cleanup, causing a local availability impact. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over memory failure injection, hwpoison handling, or memory hotplug paths. The issue is not network reachable. Impact is resource leak or cleanup blockage only, with no evidence of UAF, OOB access, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) YES SIMPLEFIX LEAK HARDWARE YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 0 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown * Availability impact realistic: +1. Repeated successful `hwpoison` accounting operations can leak references to `memory_block` devices and may interfere with memory block teardown or hotplug cleanup. * Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering normally requires control over memory failure injection, hwpoison paths, or memory hotplug behavior. * Rare and difficult-to-reach path: -1. This is not a common unprivileged syscall, networking, filesystem, or packet-processing path. * No generic memory corruption: +0. The patch fixes a missing `put_device()` after `find_memory_block_by_id()`, i.e. a reference leak. * No LPE plausibility: +0. There is no UAF, double free, OOB access, stale callback, type confusion, arbitrary write, or attacker-controlled reclaim shown. * No confidentiality or integrity impact: +0. The leaked reference can pin objects but does not expose data or modify protected state. * Call-site confidence: high. The changed helpers and the reference ownership pattern are visible in the patch. Raw score is negative after privilege and rarity penalties, so the actionable score is floored at 0. ## 3. Reachability analysis The affected path is local and tied to memory poison accounting. A normal unprivileged user is not expected to reliably invoke these helpers in typical deployments. Practical triggering usually requires administrative access to memory failure injection, hwpoison testing, or memory hotplug related operations. Namespaces or containers do not obviously lower the privilege requirement because this is not a namespaced per-container resource interface. The issue is not network reachable and is not default exposed as a high-control user API. ## 4. Severity interpretation This behaves like a low-risk resource/reference leak, not an Important-class kernel vulnerability. The realistic impact is limited availability degradation or cleanup blockage after repeated privileged operations. Theoretical escalation is not supported by the patch because there is no concrete memory corruption primitive, no stale pointer reuse, and no attacker-controlled overwrite or object replacement. ## 5. One-sentence report phrase A missing `put_device()` in memory block hwpoison accounting leaks `memory_block` device references on successful lookups, potentially causing local privileged resource leakage or hotplug cleanup issues but not memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed or handled in deferred maintenance triage because it is a local privileged reference leak with low actionable impact and no supported path to confidentiality, integrity, or privilege-escalation consequences. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drivers/base/memory: fix memory block reference leak in poison accounting Commit: 686b4283f82cd630fafd7ca9b03dfc080b3ec8fa Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=686b4283f82cd630fafd7ca9b03dfc080b3ec8fa Commit description: memblk_nr_poison_inc() and memblk_nr_poison_sub() look up a memory block via find_memory_block_by_id(), which acquires a reference to the memory block device. Both helpers use the returned memory block without dropping that reference, leaking the device reference on each successful lookup. Drop the reference after updating nr_hwpoison. Link: https://lore.kernel.org/20260428085219.1316047-3-songmuchun@bytedance.com Fixes: 5033091 ("mm/hwpoison: introduce per-memory_block hwpoison counter") Signed-off-by: Muchun Song Reviewed-by: Miaohe Lin Acked-by: Oscar Salvador Acked-by: David Hildenbrand (Arm) Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: "Huang, Ying" Cc: Naoya Horiguchi Cc: "Rafael J. Wysocki" Cc: Vishal Verma Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman Changed files: drivers/base/memory.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=686b4283f82cd630fafd7ca9b03dfc080b3ec8fa ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64182 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64182 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: unknown Paranoid ActionableScore: 0 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).