CVE-2025-39721
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
A use-after-free vulnerability was found in the Linux kernel's QAT (QuickAssist Technology) drivers. Repeated loading/unloading of a device-specific driver (e.g., qat_4xxx) in a tight loop can cause a crash when a power management interrupt fires just before driver unload, leaving a pending work item in the shared `qat_misc_wq` queue. Executing that item after driver removal dereferences freed memory, leading to a kernel panic.
Risk Assessment
The organization faces system instability and potential kernel panics during QAT driver load/unload operations, which may disrupt critical services relying on hardware acceleration.
Recommendation
Apply the Linux kernel patch that flushes the `qat_misc_wq` workqueue during device shutdown immediately. Update to a kernel version containing this fix or backport the patch manually.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: crypto: qat - flush misc workqueue during device shutdown Repeated loading and unloading of a device specific QAT driver, for example qat_4xxx, in a tight loop can lead to a crash due to a use-after-free scenario. This occurs when a power management (PM) interrupt triggers just before the device-specific driver (e.g., qat_4xxx.ko) is unloaded, while the core driver (intel_qat.ko) remains loaded. Since the driver uses a shared workqueue (`qat_misc_wq`) across all devices and owned by intel_qat.ko, a deferred routine from the device-specific driver may still be pending in the queue. If this routine executes after the driver is unloaded, it can dereference freed memory, resulting in a page fault and kernel crash like the following: BUG: unable to handle page fault for address: ffa000002e50a01c #PF: supervisor read access in kernel mode RIP: 0010:pm_bh_handler+0x1d2/0x250 [intel_qat] Call Trace: pm_bh_handler+0x1d2/0x250 [intel_qat] process_one_work+0x171/0x340 worker_thread+0x277/0x3a0 kthread+0xf0/0x120 ret_from_fork+0x2d/0x50 To prevent this, flush the misc workqueue during device shutdown to ensure that all pending work items are completed before the driver is unloaded. Note: This approach may slightly increase shutdown latency if the workqueue contains jobs from other devices, but it ensures correctness and stability.