From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46042][LOW] mm/mempolicy: fix memory leaks in weighted_interleave_auto_store() Date: Wed, 27 May 2026 15:39:33 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46042 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: c42a7efb9060d89b72708ffaf255d0002c2164a7 List-Id: CVE: CVE-2026-46042 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: mm/mempolicy: fix memory leaks in weighted_interleave_auto_store() Commit: c42a7efb9060d89b72708ffaf255d0002c2164a7 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c42a7efb9060d89b72708ffaf255d0002c2164a7 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46042 Analysis date: Wed, 27 May 2026 15:39:33 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46042 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46042 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-2026-46042 LOW CHECK 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-401;*CWE-772;**CWE-400;CWE-459;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'weighted_interleave_auto_store() can leak wi_state allocations when repeated writes keep the requested auto or manual mode unchanged or overwrite the old state without freeing it. A local privileged user can repeatedly write to the mempolicy sysfs control and gradually consume kernel memory, causing resource exhaustion. For the CVSS the PR:H is used because changing this global memory policy control normally requires administrator level sysfs write access. The issue is not network reachable and does not provide a kernel memory corruption primitive. Impact is denial of service only through memory leakage under repeated writes.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) SKIP CVE-2026-46042 SKIP The Fixes patch not applied yet, so unlikely that actual: e341f9c3c8412e57fe0042a33a2640245ecdf619 YES NO NO unknown MAYBE LOCK SIMPLEFIX LEAK LINUS MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 1. ActionableScore * Conservative score: 0 * Paranoid score: 0 * Final recommended bucket: **Ordinary Moderate / Low-like**:: 2. Signal breakdown * Availability/resource leak concern: +1. Repeated writes can leak `wi_state` allocations and gradually consume kernel memory. * Requires admin/root/CAP-level control in typical deployments: -2. The affected control is a global mempolicy sysfs write path, normally restricted to administrators. * Resource leak only. No memory corruption, UAF, double-free, OOB write, arbitrary write, info leak, or privilege escalation primitive is indicated. * No network reachability. The trigger is local sysfs configuration writes only. 3. Reachability analysis A local privileged user with write access to the weighted interleave auto sysfs control can trigger the leak by repeated writes such as `"1"` or unchanged mode updates. Ordinary unprivileged users and containers normally cannot write this global memory policy control. The affected feature is configuration-specific and introduced in newer kernels, and exploitation requires repeated local administrative writes. 4. Severity interpretation This behaves like a Low-like resource leak, not an actionable Moderate or Important vulnerability. The realistic impact is memory exhaustion only after repeated privileged operations. There is no theoretical or demonstrated memory corruption beyond leaked allocations, and no confidentiality or integrity impact. 5. One-sentence report phrase A privileged sysfs write path in `weighted_interleave_auto_store()` can leak `wi_state` allocations on repeated mode writes, causing only gradual resource-exhaustion DoS. 6. Manual review recommendation NO MANUAL CHECK NEEDED. This is a privileged resource leak with no memory corruption, no security-boundary bypass, and no remote or unprivileged trigger. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mm/mempolicy: fix memory leaks in weighted_interleave_auto_store() Commit: c42a7efb9060d89b72708ffaf255d0002c2164a7 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c42a7efb9060d89b72708ffaf255d0002c2164a7 Commit description: weighted_interleave_auto_store() fetches old_wi_state inside the if (!input) block only. This causes two memory leaks: 1. When a user writes "false" and the current mode is already manual, the function returns early without freeing the freshly allocated new_wi_state. 2. When a user writes "true", old_wi_state stays NULL because the fetch is skipped entirely. The old state is then overwritten by rcu_assign_pointer() but never freed, since the cleanup path is gated on old_wi_state being non-NULL. A user can trigger this repeatedly by writing "1" in a loop. Fix both leaks by moving the old_wi_state fetch before the input check, making it unconditional. This also allows a unified early return for both "true" and "false" when the requested mode matches the current mode. Link: https://lore.kernel.org/20260401005702.7096-1-liu.yun@linux.dev Link: https://sashiko.dev/#/patchset/20260331100740.84906-1-liu.yun@linux.dev Fixes: e341f9c ("mm/mempolicy: Weighted Interleave Auto-tuning") Signed-off-by: Jackie Liu Reviewed-by: Joshua Hahn Reviewed by: Donet Tom Cc: Gregory Price Cc: Alistair Popple Cc: Byungchul Park Cc: David Hildenbrand Cc: # v6.16+ Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman Changed files: mm/mempolicy.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=c42a7efb9060d89b72708ffaf255d0002c2164a7 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46042 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46042 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).