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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.
Fixes: e5745f3411 ("crypto: qat - enable power management for QAT GEN4")
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Ahsan Atta <ahsan.atta@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.