CVE-2024-26623: pds_core: Prevent race issues involving the adminq

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

pds_core: Prevent race issues involving the adminq

There are multiple paths that can result in using the pdsc's
adminq.

[1] pdsc_adminq_isr and the resulting work from queue_work(),
    i.e. pdsc_work_thread()->pdsc_process_adminq()

[2] pdsc_adminq_post()

When the device goes through reset via PCIe reset and/or
a fw_down/fw_up cycle due to bad PCIe state or bad device
state the adminq is destroyed and recreated.

A NULL pointer dereference can happen if [1] or [2] happens
after the adminq is already destroyed.

In order to fix this, add some further state checks and
implement reference counting for adminq uses. Reference
counting was used because multiple threads can attempt to
access the adminq at the same time via [1] or [2]. Additionally,
multiple clients (i.e. pds-vfio-pci) can be using [2]
at the same time.

The adminq_refcnt is initialized to 1 when the adminq has been
allocated and is ready to use. Users/clients of the adminq
(i.e. [1] and [2]) will increment the refcnt when they are using
the adminq. When the driver goes into a fw_down cycle it will
set the PDSC_S_FW_DEAD bit and then wait for the adminq_refcnt
to hit 1. Setting the PDSC_S_FW_DEAD before waiting will prevent
any further adminq_refcnt increments. Waiting for the
adminq_refcnt to hit 1 allows for any current users of the adminq
to finish before the driver frees the adminq. Once the
adminq_refcnt hits 1 the driver clears the refcnt to signify that
the adminq is deleted and cannot be used. On the fw_up cycle the
driver will once again initialize the adminq_refcnt to 1 allowing
the adminq to be used again.

The Linux kernel CVE team has assigned CVE-2024-26623 to this issue.


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

	Issue introduced in 6.4 with commit 01ba61b55b20 and fixed in 6.6.16 with commit 22cd6046eb21
	Issue introduced in 6.4 with commit 01ba61b55b20 and fixed in 6.7.4 with commit 5939feb63ea1
	Issue introduced in 6.4 with commit 01ba61b55b20 and fixed in 6.8-rc3 with commit 7e82a8745b95

Please see https://www.kernel.org or 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-2024-26623
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/net/ethernet/amd/pds_core/adminq.c
	drivers/net/ethernet/amd/pds_core/core.c
	drivers/net/ethernet/amd/pds_core/core.h


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/22cd6046eb2148b18990257505834dd45c672a1b
	https://git.kernel.org/stable/c/5939feb63ea1f011027576c64b68b681cbad31ca
	https://git.kernel.org/stable/c/7e82a8745b951b1e794cc780d46f3fbee5e93447