From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68175][LOW] tracing: Fix resource leak on mmiotrace trace_pipe close Date: Mon, 10 Aug 2026 19:36:27 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68175 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: f9e6dfe341fb31c95b9655eb6b1db8b3ae090817 List-Id: CVE: CVE-2026-68175 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: tracing: Fix resource leak on mmiotrace trace_pipe close Commit: f9e6dfe341fb31c95b9655eb6b1db8b3ae090817 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f9e6dfe341fb31c95b9655eb6b1db8b3ae090817 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68175 Analysis date: Mon, 10 Aug 2026 19:36:27 -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-2026-68175 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68175 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-2026-68175 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-401;*CWE-772;**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 'mmiotrace trace_pipe close can leak a header_iter allocation and keep a stale pci_dev reference because the tracer close handler is not invoked for trace_pipe release. Repeated short reads such as opening trace_pipe and closing it before the stream is completed can accumulate leaked resources and may lead to local denial of service through memory or reference exhaustion. For the CVSS the PR:H is used for the paranoid score because mmiotrace and tracing control normally require administrative privileges on the target system. The issue is not network reachable and has no evident memory corruption primitive. Impact is availability loss only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) YES TRACE LEAK UAF LINUS NO 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 short reads of `trace_pipe` with `mmiotrace` active can leak `header_iter` allocations and retain `pci_dev` references. * Reliable resource exhaustion concern: +1 in the paranoid interpretation only. The commit explicitly says repeated `head -n 1 /sys/kernel/tracing/trace_pipe` can trigger a massive leak. * Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2. Enabling and using `mmiotrace` and accessing tracing/tracefs normally requires administrative privileges. * Rare and non-default tracer path: -1. `mmiotrace` is a specialized tracing mode, not a default production data path. * No memory corruption signal: +0. This is a resource/reference leak, not UAF, double-free, OOB write, type confusion, or arbitrary write. * No confidentiality or integrity signal: +0. The patch does not expose data or modify protected state beyond leaking resources. Call-site confidence: high. The commit directly explains that `tracing_release_pipe()` calls `.pipe_close`, while `mmio_close()` was only wired to `.close`. 3. **Reachability analysis** The bug is local and requires access to kernel tracing interfaces with the `mmiotrace` tracer active. In normal deployments this is restricted to root or a process with equivalent tracing privileges. Containers and namespaces usually do not make this reachable unless tracefs or debugfs is deliberately exposed with elevated permissions. The path is not network reachable and is not enabled by default in typical production systems. 4. **Severity interpretation** This behaves like a Low-like or ordinary Moderate resource exhaustion issue. The realistic impact is local availability degradation through repeated resource leaks. There is no demonstrated memory corruption primitive, no privilege escalation path, and no sensitive data exposure. Even the paranoid interpretation remains below Actionable Moderate because the trigger is privileged and the affected tracer is specialized. 5. **One-sentence report phrase** `mmiotrace trace_pipe close can leak a header_iter allocation and retain a pci_dev reference when pipe_close is not wired to mmio_close, allowing a privileged local user to cause resource exhaustion by repeatedly opening and closing trace_pipe early.` 6. **Manual review recommendation** NO MANUAL CHECK NEEDED. This can be auto-closed for urgent triage purposes because it is a privileged local resource leak in a non-default tracing mode, with no memory corruption, no network exposure, and no plausible privilege escalation evidence. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: tracing: Fix resource leak on mmiotrace trace_pipe close Commit: f9e6dfe341fb31c95b9655eb6b1db8b3ae090817 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f9e6dfe341fb31c95b9655eb6b1db8b3ae090817 Commit description: The mmiotrace tracer was added May 12th 2008. At that time, resources created in pipe_open() could not be freed because there was not pipe_close function pointer of the tracer. The pipe_close function pointer was added in December 7th, 2009, but the mmiotrace tracer was not updated. mmio_pipe_open() allocates a header_iter and takes a pci_dev reference when trace_pipe is opened. mmio_close() frees them, but it was only wired to the tracer's .close callback. tracing_release_pipe() invokes .pipe_close, not .close, when the trace_pipe file is released. As a result, closing trace_pipe with the mmiotrace tracer active leaked the header_iter allocation and left a stale pci_dev reference. Set .pipe_close to mmio_close, matching how function_graph wires both callbacks to the same handler. Note, if the trace_pipe is read to completion, it will clean up the resources, but if one were to run: # head -n 1 /sys/kernel/tracing/trace_pipe VERSION 20070824 Over and over again, it would trigger a massive leak. Cc: stable@vger.kernel.org Fixes: c521efd ("tracing: Add pipe_close interface) Link: https://patch.msgid.link/20260715143604.14481-1-gaikwad.dcg@gmail.com Signed-off-by: deepakraog Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman Changed files: kernel/trace/trace_mmiotrace.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=f9e6dfe341fb31c95b9655eb6b1db8b3ae090817 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68175 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68175 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).