From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72104][LOW] dm-pcache: reject option groups without values commit d9c631e3fbd44246a2be781d26cfacbb9b8ec127 upstream. Date: Sat, 15 Aug 2026 16:06:26 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72104 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: 1247615aadb74c89c1b2f01a6de7df9dab92ecb3 List-Id: CVE: CVE-2026-72104 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: dm-pcache: reject option groups without values commit d9c631e3fbd44246a2be781d26cfacbb9b8ec127 upstream. Commit: 1247615aadb74c89c1b2f01a6de7df9dab92ecb3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1247615aadb74c89c1b2f01a6de7df9dab92ecb3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72104 Analysis date: Sat, 15 Aug 2026 16:06:26 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A malformed dm-pcache device-mapper table can omit the value for cache_mode or data_crc, causing a NULL pointer dereference during option parsing and a local denial of service, typically requiring administrative device-mapper control. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72104 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72104 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-2026-72104 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:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference in dm_pcache option parsing can occur when a malformed device mapper table declares an optional argument but provides only the option name without its value. The parser can consume cache_mode or data_crc and then call dm_shift_arg for the missing value, which returns NULL and is later passed to strcmp. For the CVSS the PR:L is used in the paranoid interpretation because some environments delegate device mapper control to storage services, containers, or reduced capability administrators, although normal dmsetup table loading usually requires CAP_SYS_ADMIN. The issue is local and is not network reachable. Impact is denial of service via kernel oops or crash during target construction, with no supported confidentiality or integrity primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) SKIP CVE-2026-72104 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE DISK HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - 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 Triggered signals: * Reliable kernel crash / strong DoS: +1 The malformed dm-pcache table can cause dm_shift_arg() to return NULL, followed by strcmp(NULL, ...), producing a NULL pointer dereference during target construction. * Important filesystem/storage path: +1 in paranoid view only The affected code is in device-mapper storage target setup, but the bug is limited to parsing invalid target options and does not affect storage metadata integrity or data-plane writes. Subtracted signals: * Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2 Loading or changing device-mapper tables normally requires root or CAP_SYS_ADMIN via dmsetup or equivalent access to /dev/mapper/control. * Rare / non-default target path: -1 in conservative view dm-pcache is a specific device-mapper target and the trigger requires constructing a malformed table for that target. Not triggered: * No local unprivileged trigger in typical deployments. * No remote or network reachability. * No UAF, double-free, OOB write, arbitrary write, refcount abuse, type confusion, or page-cache corruption. * No confidentiality or integrity primitive. * No plausible privilege escalation from the patch context. Call-site confidence: high. The vulnerable parser path and the NULL dereference condition are directly described by the commit and visible in the patch. ## 3. Reachability analysis The bug is triggered by submitting a malformed dm-pcache device-mapper table where a recognized option such as cache_mode or data_crc is provided without its required value. In normal deployments, this requires administrative storage management privileges, typically root or CAP_SYS_ADMIN. A reduced-capability storage service or containerized environment with delegated device-mapper control could lower the practical privilege boundary, but this is not the default model and does not make the issue broadly unprivileged. The path is local only and not network-triggerable. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like local DoS issue. The realistic impact is a kernel oops or crash during invalid target construction. Theoretical impact does not extend beyond DoS because the patch shows a NULL pointer dereference from missing argument validation, not a memory corruption primitive with attacker-controlled reuse, overwrite, disclosure, or privilege escalation potential. ## 5. One-sentence report phrase A malformed dm-pcache device-mapper table can omit the value for cache_mode or data_crc, causing a NULL pointer dereference during option parsing and a local denial of service, typically requiring administrative device-mapper control. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This is a validation-only NULL pointer dereference in a privileged local storage configuration path, with no supported confidentiality, integrity, or privilege-escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dm-pcache: reject option groups without values commit d9c631e3fbd44246a2be781d26cfacbb9b8ec127 upstream. Commit: 1247615aadb74c89c1b2f01a6de7df9dab92ecb3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1247615aadb74c89c1b2f01a6de7df9dab92ecb3 Commit description: The pcache target parses optional arguments as name/value pairs. A table that advertises one optional argument and supplies only a recognized option name, for example "cache_mode", reaches parse_cache_opts() with argc == 1. The parser consumes the name, decrements argc to zero, then calls dm_shift_arg() again for the value. dm_shift_arg() returns NULL when no arguments remain, and the following strcmp() dereferences that NULL pointer. Check that each recognized option has a value before consuming it. This keeps valid "cache_mode writeback" and "data_crc true/false" tables unchanged while making malformed tables fail during target construction with a precise missing-value error. Assisted-by: Codex:gpt-5.5-cyber-preview Signed-off-by: Samuel Moelius Reviewed-by: Zheng Gu Signed-off-by: Mikulas Patocka Fixes: 1d57628ff95b ("dm-pcache: add persistent cache target in device-mapper") Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Diffstat -rw-r--r-- drivers/md/dm-pcache/dm_pcache.c 8 Changed files: drivers/md/dm-pcache/dm_pcache.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=1247615aadb74c89c1b2f01a6de7df9dab92ecb3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72104 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72104 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:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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).