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.