CVE-2026-68084 Overview
CVE-2026-68084 identifies a memory leak in the Linux kernel's vme_user staging driver, specifically within the tsi148 VME bridge implementation. The tsi148_probe() function allocates a location monitor resource and links it into the tsi148_bridge->lm_resources list. The corresponding tsi148_remove() function frees only the DMA, slave, and master resource lists, leaving the location monitor resource allocated when the device is unbound or the module is unloaded. Repeated module load and unload cycles progressively consume kernel memory.
Critical Impact
The unbalanced resource cleanup path leaks kernel memory on every device unbind or module unload of the tsi148 VME bridge driver, contributing to long-term resource exhaustion on affected systems.
Affected Products
- Linux kernel staging/vme_user subsystem
- tsi148 VME bridge driver
- Multiple upstream stable branches referenced in the kernel git commits
Discovery Timeline
- 2026-08-10 - CVE-2026-68084 published to NVD
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-68084
Vulnerability Analysis
The defect is a classic asymmetric resource management flaw in a Linux kernel driver. During probe, tsi148_probe() builds four resource lists on the bridge structure: DMA, slave, master, and location monitor (lm_resources). The probe error path correctly unwinds all four lists. The teardown path in tsi148_remove() diverges from probe and releases only three of them.
Because lm_resources is never traversed and freed in the remove path, every kernel object linked to that list persists after tsi148_bridge itself is deallocated. The leaked objects become unreachable, and their memory cannot be reclaimed without a system reboot. The fix walks and frees the lm_resources list in tsi148_remove() before releasing the bridge structure.
Root Cause
The root cause is an incomplete cleanup routine. The remove path does not mirror the allocations performed during probe. This produces a Memory Leak [CWE-401] each time the driver detaches from a Tundra Semiconductor tsi148 VME bridge device or the module is unloaded.
Attack Vector
Triggering the leak requires the ability to bind and unbind the tsi148 driver or to load and unload the module. This is a local operation typically restricted to privileged users. The vulnerability does not provide code execution or information disclosure. It degrades system availability over time on hosts that repeatedly cycle the driver.
No public exploitation code is required. The condition is reproduced by normal driver lifecycle operations against affected kernels. See the upstream fix commit for the exact source-level change.
Detection Methods for CVE-2026-68084
Indicators of Compromise
- Growth in kernel slab allocations attributable to the vme subsystem across driver load and unload cycles
- Repeated modprobe vme_tsi148 and rmmod vme_tsi148 events in system logs on hosts with VME hardware
- Increasing unreclaimable kernel memory (SUnreclaim in /proc/meminfo) on long-running systems with the tsi148 driver
Detection Strategies
- Track kernel version and staging driver inclusion across the Linux fleet and flag hosts running unpatched builds that expose vme_user and vme_tsi148.
- Correlate module load and unload telemetry with kernel memory growth trends to identify systems that cycle the affected driver.
- Review vendor security bulletins for the six referenced kernel git commits and map them to the distribution kernels in use.
Monitoring Recommendations
- Baseline kernel slab consumption on hosts with VME bridge hardware and alert on sustained upward drift.
- Monitor process auditing (auditd) for init_module and delete_module syscalls targeting vme_tsi148.
- Aggregate kernel version inventory to prioritize patch rollout on systems that expose the affected driver.
How to Mitigate CVE-2026-68084
Immediate Actions Required
- Apply the upstream Linux kernel patch that frees lm_resources inside tsi148_remove() before tsi148_bridge deallocation.
- Update to a distribution kernel that incorporates one of the referenced stable commits, including 151edde741f8, 18be0ad31b16, or eef048dd77eb.
- Restrict privileged access to module loading on systems where the driver is present but not required.
Patch Information
The fix is merged upstream and backported across multiple stable branches. Refer to the Linux kernel stable tree and the six commit hashes published in the NVD references for the exact kernel versions that ship the corrected tsi148_remove() implementation.
Workarounds
- Blacklist the vme_tsi148 module on hosts that do not require VME bridge functionality by adding blacklist vme_tsi148 to /etc/modprobe.d/.
- Avoid repeated bind and unbind cycles of the tsi148 driver on unpatched kernels to limit cumulative memory loss.
- Schedule maintenance reboots on affected long-running systems until the kernel patch is deployed.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
