From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98848][LOW] rtc: ac100: Assign .num before accessing .hws Date: Sat, 24 Oct 2026 12:55:28 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98848 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: 6bb55381daf1a1bed0657189a1396e7467712525 List-Id: CVE: CVE-2026-98848 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: rtc: ac100: Assign .num before accessing .hws Commit: 6bb55381daf1a1bed0657189a1396e7467712525 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6bb55381daf1a1bed0657189a1396e7467712525 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98848 Analysis date: Sat, 24 Oct 2026 12:55:28 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: Late counted-by metadata initialization can trigger UBSAN during AC100 probe despite all stores remaining within the allocated array. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98848 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98848 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-2026-98848 LOW https://www.kernelcve.org/list/?q=CVE-2026-98848 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-665;*CWE-457;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'The AC100 RTC clock registration path accesses clk_data hws while the __counted_by field clk_data num is still zero. The backing allocation already contains AC100_CLKOUT_NUM entries, so this is a sanitizer metadata initialization error rather than a real out of bounds write. With CONFIG_UBSAN_BOUNDS it produces a bounds report during device probe, and with CONFIG_UBSAN_TRAP the first store can trap and cause probe failure or a kernel oops. For the CVSS the PR:H value reflects that reliable retriggering normally requires administrative control over driver binding or device probing. There is no supported confidentiality impact, integrity impact, UAF, or privilege escalation primitive. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.1 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 2.7 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE KASAN OOB SIMPLEFIX LINUS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 0 (+1 plausible trap/Oops, -1 specialized sanitizer/compiler configuration). * Conservative score: 0; no floor or cap applied. * Raw paranoid score: 0. * Paranoid score: 0; stronger consequences are unsupported. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Reliable kernel crash/strong DoS: with `CONFIG_UBSAN_BOUNDS`, counted-by-aware compiler support, and `CONFIG_UBSAN_TRAP`, the first store can trap during device probe. * -1 Non-default configuration: the fault requires a new compiler implementing `__counted_by` bounds checking plus UBSAN bounds instrumentation; trapping additionally requires `CONFIG_UBSAN_TRAP`. * The backing allocation already has `AC100_CLKOUT_NUM` entries. Only the sanitizer's current logical bound is zero because `.num` is initialized late; no physical heap OOB write is shown. * No UAF, retry accumulation, shared-backing write, authorization bypass, protected-state corruption, disclosure, or integrity primitive is present. * B5-R does not apply: there is no heap/slab OOB write, retry accumulation, attacker-influenced retry sequence, or later consumption of corrupted state. * Extra availability, C/I, and LPE points are not awarded. 3. Reachability analysis The path runs while probing AC100 RTC hardware. No attacker-invocable data path or below-host-admin trigger is established. Administrative driver rebinding might retrigger probe, but the supplied source does not prove that this is the only trigger; therefore host-admin and UID-0 requirements remain unknown. No namespace capability, remote input, race, or prior attacker-controlled object setup is shown. 4. Primitive and severity reading The exact defect is late initialization of counted-by metadata before valid in-allocation array stores. It can cause a sanitizer report or trap, but it does not write outside the allocated `hws[]` storage. This is CLASS_C configuration-dependent fault behavior, not memory corruption. The fix changes initialization order without changing successful provider behavior. ImportantCandidate is NO and automatic downgrade is allowed because no unresolved corruption or trust-boundary primitive remains. 5. One-sentence report phrase Late counted-by metadata initialization can trigger UBSAN during AC100 probe despite all stores remaining within the allocated array. 6. Manual review advice NO MANUAL CHECK NEEDED The patch and commit explicitly establish a sanitizer metadata false positive rather than a real out-of-bounds access. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: rtc: ac100: Assign .num before accessing .hws Commit: 6bb55381daf1a1bed0657189a1396e7467712525 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6bb55381daf1a1bed0657189a1396e7467712525 Commit description: Commit f316cdf ("clk: Annotate struct clk_hw_onecell_data with __counted_by") annotated the hws member of 'struct clk_hw_onecell_data' with __counted_by, which informs the bounds sanitizer (UBSAN_BOUNDS) about the number of elements in .hws[], so that it can warn when .hws[] is accessed out of bounds. As noted in that change, the __counted_by member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. This occurs in ac100_rtc_register_clks() due to .num being assigned only after every clkout clock has been stored in .hws[]. With CONFIG_UBSAN_BOUNDS and a compiler that implements __counted_by (GCC 15.1+ or Clang 20.1+), this triggers an array-index-out-of-bounds report during probe, and with CONFIG_UBSAN_TRAP the first store traps. Initialize .num with AC100_CLKOUT_NUM, the number of elements .hws[] was allocated with, right after the allocation. That is the value the loop counter ends up at on the success path anyway, so the provider's behaviour is unchanged. Cc: stable@vger.kernel.org Fixes: f316cdf ("clk: Annotate struct clk_hw_onecell_data with __counted_by") Assisted-by: LLM Signed-off-by: Aamir Ahmed Reviewed-by: Chen-Yu Tsai Reviewed-by: Gustavo A. R. Silva Link: https://patch.msgid.link/AS8P251MB00013E724A77A355668B6CCEC8B42@AS8P251MB0001.EURP251.PROD.OUTLOOK.COM Signed-off-by: Alexandre Belloni Signed-off-by: Greg Kroah-Hartman Changed files: drivers/rtc/rtc-ac100.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=6bb55381daf1a1bed0657189a1396e7467712525 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98848 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98848 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:H/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.1 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).