Subject: CVE-2022-48867: dmaengine: idxd: Prevent use after free on completion memory

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

dmaengine: idxd: Prevent use after free on completion memory

On driver unload any pending descriptors are flushed at the
time the interrupt is freed:
idxd_dmaengine_drv_remove() ->
	drv_disable_wq() ->
		idxd_wq_free_irq() ->
			idxd_flush_pending_descs().

If there are any descriptors present that need to be flushed this
flow triggers a "not present" page fault as below:

 BUG: unable to handle page fault for address: ff391c97c70c9040
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page

The address that triggers the fault is the address of the
descriptor that was freed moments earlier via:
drv_disable_wq()->idxd_wq_free_resources()

Fix the use after free by freeing the descriptors after any possible
usage. This is done after idxd_wq_reset() to ensure that the memory
remains accessible during possible completion writes by the device.

The Linux kernel CVE team has assigned CVE-2022-48867 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.19 with commit 63c14ae6c161 and fixed in 6.1.8 with commit b9e8e3fcfec6
	Issue introduced in 5.19 with commit 63c14ae6c161 and fixed in 6.2 with commit 1beeec45f9ac

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-48867
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/dma/idxd/device.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/b9e8e3fcfec625fc1c2f68f684448aeeb882625b
	https://git.kernel.org/stable/c/1beeec45f9ac31eba52478379f70a5fa9c2ad005