From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74334][MODERATE 7.0] RDMA/nldev: Fix locking when accessing mr->pd [ Upstream Date: Sat, 15 Aug 2026 19:57:11 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74334 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 1a132ee4e655288d9a0937ea5109a0d038431ae9 List-Id: CVE: CVE-2026-74334 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: RDMA/nldev: Fix locking when accessing mr->pd [ Upstream Commit: 1a132ee4e655288d9a0937ea5109a0d038431ae9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a132ee4e655288d9a0937ea5109a0d038431ae9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74334 Analysis date: Sat, 15 Aug 2026 19:57:11 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: RDMA nldev resource dumps can race with MR reregistration and read a stale `mr->pd` pointer after the old protection domain reference is dropped, creating a local UAF-style kernel crash risk and a paranoid privilege-escalation concern that requires manual review. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74334 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74334 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: MODERATE 7.0 Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74334 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'RDMA/nldev resource dumps can race with ib_uverbs_rereg_mr when a memory region is moved to another protection domain. The dump path may read mr pd while the reregistration path replaces that pointer and later drops the old protection domain reference, creating a stale pointer and use-after-free candidate in kernel memory. For the CVSS the PR:L is used because reliable triggering requires a local user or process with access to RDMA uverbs and netlink resource dump interfaces, not full administrator privileges in all deployments. The issue is not directly network reachable and is driven by local control plane operations rather than RDMA packet traffic. Impact is at least local denial of service via kernel crash and in the paranoid case may allow confidentiality or integrity impact due to UAF style memory corruption, so it should be manually reviewed.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES READ LOCK DANGER INIT NETWORK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown * Local unprivileged trigger: +1 A local process with access to RDMA uverbs and RDMA netlink resource dump paths can potentially race `ib_uverbs_rereg_mr()` against `nldev` MR dumping. * Memory corruption, weak/indirect corruption candidate: +1 The patch addresses racy access to `mr->pd`, which can change during `rereg_mr`. The old PD can be dropped while `nldev` is still reading through the stale pointer. This is a UAF candidate, but the patch does not show attacker-controlled reclaim, overwrite, callback control, or type confusion. * Real lifetime corruption: +1 The new `rdma_restrack_sync()` acts as a lifetime fence, waiting for old netlink dump users before the old PD reference is dropped. That strongly indicates a real object lifetime race rather than a pure bookkeeping issue. * Reliable kernel crash / strong DoS: +1 A stale `mr->pd` dereference in the kernel resource dump path can plausibly crash the kernel. * Local device object lifetime API concern: +1 paranoid only RDMA uverbs plus nldev exposes user-created kernel objects and this patch specifically involves object lifetime and reference ordering. This is enough for paranoid manual-review elevation, but not enough to infer strong LPE. * Hard or unreliable race / special timing required: -1 conservative Exploitation requires racing MR reregistration with concurrent netlink resource dumping. There is no demonstrated reclaim or stable exploitation primitive in the patch. ## 3. Reachability analysis The bug is locally reachable on systems with RDMA support and accessible `/dev/infiniband/uverbs*` plus RDMA netlink resource interfaces. It is not directly network reachable through RDMA packet traffic. In many deployments RDMA uverbs access may be granted to non-root HPC, storage, or service users, so PR:L is more realistic than PR:H when such users can create and reregister MRs. Namespaces and containers may matter if RDMA devices are passed through or delegated, but typical host exposure still depends on device permissions and RDMA stack availability. ## 4. Severity interpretation This is more than an ordinary Moderate cleanup because it fixes a real lifetime race around `mr->pd` and introduces an explicit synchronization primitive to fence old netlink users. Realistic impact is most clearly local kernel crash / DoS. Theoretical escalation is not proven because the patch does not show attacker-controlled reclaim, writable stale access, callback dispatch, or type confusion. Therefore this is best treated as Actionable Moderate at minimum, with manual review required due to UAF-style lifetime corruption. ## 5. One-sentence report phrase RDMA nldev resource dumps can race with MR reregistration and read a stale `mr->pd` pointer after the old protection domain reference is dropped, creating a local UAF-style kernel crash risk and a paranoid privilege-escalation concern that requires manual review. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK. Reason: this is a race-dependent lifetime bug with a plausible stale pointer / UAF path in kernel memory, even though the provided patch does not demonstrate a strong exploit primitive beyond DoS. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: RDMA/nldev: Fix locking when accessing mr->pd [ Upstream Commit: 1a132ee4e655288d9a0937ea5109a0d038431ae9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a132ee4e655288d9a0937ea5109a0d038431ae9 Changed files: drivers/infiniband/core/nldev.c drivers/infiniband/core/restrack.c drivers/infiniband/core/restrack.h drivers/infiniband/core/uverbs_cmd.c include/rdma/ib_verbs.h 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=1a132ee4e655288d9a0937ea5109a0d038431ae9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74334 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74334 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:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: 4 Paranoid ActionableScore: 5 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: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE 7.0 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).