CVE-2024-26623

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.