CVE-2025-39721

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.

Affected Software

References

• https://git.kernel.org/stable/c/3d4df408ba9bad2b205c7fb8afc1836a6a4ca88a
• https://git.kernel.org/stable/c/5858448a6c65d8ee3f8600570d3ce19febcb33be
• https://git.kernel.org/stable/c/e59a52e429e13df3feb34f4853a8e36d121ed937
• https://git.kernel.org/stable/c/fe546f5c50fc474daca6bee72caa7ab68a74c33d