A recently published Linux kernel patch addresses a race condition in the regulator core that could produce a local use-after-free (UAF), duplicate alias entries, or inconsistent supply mappings — filed as CVE-2025-68354 — by protecting the regulator_supply_alias_list with the existing regulator_list_mutex.
The Linux regulator framework provides a unified API for voltage/current regulator devices and the drivers that consume those supplies. It includes helper functions such as regulator_register_supply_alias, regulator_unregister_supply_alias, and regulator_supply_alias, which together manage name-based alias mappings used when a consumer driver looks up the regulator that supplies a specific pin or rail. These aliases are stored in an internal list commonly referred to as regulator_supply_alias_list. Historically, other parts of the regulator core have used a global mutex named regulator_list_mutex to protect concurrent modifications of regulator data structures. The newly disclosed issue shows that some code paths that traverse and modify the alias list did so without acquiring that mutex, opening a window for concurrency bugs. The kernel project issued fixes that add or reintroduce mutex protection around all traversals, insertions and deletions on the alias list.
Caution: the upstream commit links and the detailed patch diffs are published in the kernel stable tree. Those patch diffs are the authoritative technical record of what changed; operators and developers who need to backport or audit the fix should consult the upstream commits or the distribution’s security advisory for the exact patch and the vendor-specific mitigation timeline. Conclusion: CVE-2025-68354 is a classic concurrency bug fixed with conservative locking. It’s not an exotic zero-day but it’s the kind of low-level kernel correctness issue that deserves rapid, coordinated response: patch upstream or via your distro, validate in staging, and deploy to production, especially where local code execution is possible.
Source: MSRC Security Update Guide - Microsoft Security Response Center
Background
The Linux regulator framework provides a unified API for voltage/current regulator devices and the drivers that consume those supplies. It includes helper functions such as regulator_register_supply_alias, regulator_unregister_supply_alias, and regulator_supply_alias, which together manage name-based alias mappings used when a consumer driver looks up the regulator that supplies a specific pin or rail. These aliases are stored in an internal list commonly referred to as regulator_supply_alias_list. Historically, other parts of the regulator core have used a global mutex named regulator_list_mutex to protect concurrent modifications of regulator data structures. The newly disclosed issue shows that some code paths that traverse and modify the alias list did so without acquiring that mutex, opening a window for concurrency bugs. The kernel project issued fixes that add or reintroduce mutex protection around all traversals, insertions and deletions on the alias list. What the CVE actually says
- Vulnerability identifier: CVE-2025-68354.
- Component: Linux kernel regulator core (drivers/regulator/core.c and related code).
- Root cause: regulator_supply_alias_list was accessed without locking in regulator_supply_alias, regulator_register_supply_alias, and regulator_unregister_supply_alias.
- Consequences described by the maintainer: concurrent registration, unregistration and lookups can race and lead to (1) a use-after-free if an alias entry is removed while another thread is reading it, (2) duplicate alias entries if two threads register the same alias concurrently, and (3) inconsistent alias mappings observed by other consumers.
- Fix: protect all list traversals, insertions and deletions with the existing regulator_list_mutex.
Technical analysis: why the race matters
Race conditions in kernel lists are dangerous
Kernel code commonly uses linked lists and other shared structures without GC; when one thread removes and frees an element while another thread is reading it, the reader can dereference memory that has been reclaimed. This classic pattern is a use-after-free that can cause crashes (kernel panics) or — in more sophisticated scenarios — memory corruption exploitable for privilege escalation, code execution, or denial-of-service. The regulator alias list is not normally exposed over the network, so the expected attack vector is local, but that still represents meaningful risk for multi-process or multi-threaded systems, containers running privileged code, and complex driver stacks.Specific functions implicated
- regulator_supply_alias: looks up an alias mapping for a device/supply pair. If it iterates the alias list without locking, a concurrent deletion can free the entry underneath the lookup.
- regulator_register_supply_alias: creates a new alias entry. Without locking, two concurrent registrations for the same alias may both succeed and insert duplicate nodes.
- regulator_unregister_supply_alias: removes an alias mapping. Without synchronized removal, concurrent readers may observe inconsistent state or attempt to access freed memory.
Severity and exploitability
Public vulnerability trackers that aggregated the kernel announcement rate this as a moderate or medium severity issue (CVSS v3.1 score commonly shown at 5.5 in vendor trackers). The attack vector is local, and privileges required are low, with no confidentiality or integrity impact listed but high availability impact possible (system hangs or kernel panics). Some trackers show a very low EPSS (exploit probability) for the near term, suggesting little evidence of active exploitation as of publication. That said, race-condition bugs are sometimes used by attackers with local access to cause denial-of-service or to escalate privileges in combination with other issues.Which systems are affected
The CVE was filed by the Linux kernel project against upstream kernel code and therefore applies to kernel trees and releases that include the vulnerable commit(s). Upstream metadata identifies the problem in drivers/regulator/core.c and lists the fix commits in the stable tree. Distribution vendors will backport the upstream fixes into their kernels and ship updates for affected releases. Debian’s package tracker and other distributions have mapped affected package versions and have started to prepare fixes or mark them as pending. Because the regulator subsystem is widely used across architectures and platforms (desktop, server, embedded devices, SoCs), the practical attack surface depends on whether a given platform exposes the regulator API to code that an attacker can control locally (e.g., untrusted kernel modules, drivers, or privileged but untrusted userspace components). Embedded devices or systems where many drivers register/unregister aliases dynamically are likely to be more exposed to race timing windows.What the patch changes (high-level)
The upstream fix does not rework the regulator core; instead, maintainers applied defensive locking by:- Ensuring that all list traversals over regulator_supply_alias_list acquire regulator_list_mutex first.
- Wrapping both insert and delete code paths with the same mutex so that reads cannot see intermediate or freed nodes.
- Harmonizing the API behavior so that duplicate registrations and inconsistent mappings are prevented by guarding the recognition and insertion logic with the lock.
Real-world impact: where this matters
- Servers and desktops: typical distributions with long-lived stable kernels are likely to ship fixes in point releases. On servers, local privilege escalation is the main concern. If an attacker already has local code execution at user privilege, exploiting a UAF might allow escalation to root in certain setups. The reported CVE description does not claim an immediate privilege escalation vector, but UAFs in kernel code routinely provide that possibility in practice under the right conditions.
- Embedded and SoC platforms: devices with many dynamic regulator alias registrations (complex SoCs, mobile phones, IoT gateways) may trigger alias registration/unregistration frequently during device probing, runtime power management changes, or hotplug events. A race here can result in kernel crashes and service outages on devices where uptime is crucial.
- Containers and multi-tenant hosts: while containers isolate userspace, the kernel is shared. If a containerized workload can exercise driver registration code paths (via privileged helpers or device passthrough), a race could be induced from within the container and cause host kernel instability. Admins should avoid exposing devices that permit untrusted workloads to trigger kernel-level registration operations.
Vendor and distribution response
Upstream kernel commits are available and referenced in the CVE metadata; distribution maintainers (Debian, SUSE, Red Hat and others) track the issue and will or have issued advisories listing affected package versions and patched updates. The Debian tracker, for example, enumerates affected kernel package versions and shows backporting activity. SUSE and other vendors list the CVE and tag it as moderate. Monitoring distribution security pages and package feeds is the correct operational path for most administrators. Some vendors may choose to backport only the minimal fix into their stable kernels rather than escalating to a new major kernel version. That is standard practice and typically sufficient: the fix is defensive locking in the core, which is safe to backport as a small patch. Administrators should watch their vendor’s security advisory feed for the patch release and CVE references.Detection, proof-of-concept, and exploitation
At publication time there are no widely published proofs-of-concept demonstrating privilege escalation or remote compromise via this CVE. Trackers show a low EPSS and no KEV (Known Exploited Vulnerabilities) listing, indicating no public evidence of active exploitation. Race conditions can be non-trivial to exploit and frequently require careful timing and local code execution privileges; however, the possibility of denial-of-service via kernel crashes is immediate and plausible. Systems that must prove resilience can test for regressions by running stress tests and syzkaller or KCSAN-like fuzzers targeting regulator registration/unregistration paths. Reproducers for similar regulator/list races historically come from syzbot reports — automated fuzzing services that test kernel APIs — so using those tools in test environments can increase confidence in the fix. Note that fuzz testing requires an isolated lab; never run destructive fuzzers on production systems.Recommended mitigation and operational checklist
- Identify affected systems.
- Inventory kernel versions across servers, desktops, and embedded devices. Look for kernels built from upstream trees where the vulnerable commit range (introduced commit -> fixed commit) applies. Distribution trackers (Debian, SUSE, Red Hat) can map package versions for you.
- Prioritize updates.
- Schedule kernel updates for hosts where local privilege exposure is higher (multi-user servers, developer workstations, systems with untrusted local code). For embedded devices, coordinate vendor firmware/kernel updates.
- Apply vendor patches or upgrade kernels.
- Use the distribution’s security advisories and packages. If you maintain custom kernels, merge the upstream fix commits and rebuild. The upstream fix is limited to locking the alias list; backports are widely acceptable.
- Test before deployment.
- Run kernel regression tests and stress scenarios focusing on regulator operations, device probing, and power-management flows. Use a staging environment identical to production where possible.
- Reduce attack surface in the meantime.
- Avoid exposing device controls that allow untrusted code to register/unregister aliases. Restrict access to privileged container runtimes and limit device passthrough to trusted workloads.
- Monitor and audit.
- Watch vendor advisories, kernel mailing lists, and CVE feeds for updated information. If anomalous kernel crashes or regulator-related oops messages appear in logs, escalate them to engineering for immediate patching and troubleshooting.
Patch analysis: trade-offs and risks
The patch strategy — protect the alias list with the existing regulator_list_mutex — is conservative and correct. It lowers the risk of races by serializing access to the list. However, adding mutex protection is not entirely free:- Performance cost: mutex acquisition around list traversals could add contention in workloads that register/unregister aliases at very high rates. In most systems this will be negligible; regulators are not typically a hot path.
- Deadlock risk: introducing locks or extending lock scopes can expose latent deadlocks if the locking order with other mutexes is not carefully honored. Using the same established mutex reduces that risk versus inventing a second lock. Maintaining minimal lock scope is important and the upstream patch keeps the changes localized.
- Backport complexity: maintainers backporting to older stable kernels must ensure the lock exists with the same semantics; if earlier kernels use different regulator internals, the backport may need adaptions. Distribution maintainers are already handling these backports.
For kernel developers: what to look for going forward
- Treat shared lists and registration APIs as requiring explicit synchronization. Audits that look for list traversal without locking in the regulator core (and other subsystems) are worthwhile.
- Consider tool-assisted checks: kernel sanitizers (KCSAN), syzbot fuzzing, and formalized locking order documentation can catch concurrency errors earlier. The regulator subsystem interacts with device probing and power-management, both areas where concurrency is frequent during boot or runtime reconfiguration.
Final assessment and timeline
CVE-2025-68354 is a targeted, local kernel race reported and fixed in upstream Linux tree commits. The vulnerability is consequential as a classic kernel use-after-free vector and can lead to denial-of-service or, in chained exploit scenarios, privilege escalation. At the time of disclosure there is limited or no public evidence of active exploitation and a low EPSS, but the issue is important enough that distributions have catalogued it and begun backporting or issuing advisories. Administrators should treat this as a routine but urgent kernel patching task: identify affected kernels, test updates, and deploy patched kernels in environments where untrusted local code or device passthrough creates greater exposure.Quick reference — practical steps now
- Check your distribution’s security feed for CVE-2025-68354 advisories and updated kernel packages.
- If you build custom kernels, merge the upstream fix commits referenced in the CVE metadata and rebuild; test with regulator-heavy device scenarios.
- For devices where kernel updates are slow or unavailable, reduce local attack surface (restrict privileged containers, disable unnecessary device passthrough).
Caution: the upstream commit links and the detailed patch diffs are published in the kernel stable tree. Those patch diffs are the authoritative technical record of what changed; operators and developers who need to backport or audit the fix should consult the upstream commits or the distribution’s security advisory for the exact patch and the vendor-specific mitigation timeline. Conclusion: CVE-2025-68354 is a classic concurrency bug fixed with conservative locking. It’s not an exotic zero-day but it’s the kind of low-level kernel correctness issue that deserves rapid, coordinated response: patch upstream or via your distro, validate in staging, and deploy to production, especially where local code execution is possible.
Source: MSRC Security Update Guide - Microsoft Security Response Center
