[PATCH 1/2] PCI: dwc: Guard RAS DES debugfs deinit

[Shuvam Pandey]

Hi Bjorn,

> I guess this prevents a NULL pointer dereference, right?

Yes. This is in the CONFIG_PCIE_DW_DEBUGFS teardown path when the
controller does not advertise the RAS DES capability.

In that case dwc_pcie_rasdes_debugfs_init() returns 0 before allocating
pci->debugfs->rasdes_info or initializing reg_event_lock. Later,
dwc_pcie_debugfs_deinit() still calls dwc_pcie_rasdes_debugfs_deinit()
unconditionally.

With CONFIG_DEBUG_MUTEXES, mutex_destroy() dereferences the mutex, so
calling it via &rinfo->reg_event_lock when rinfo is NULL would
dereference NULL. Without CONFIG_DEBUG_MUTEXES, mutex_destroy() is a
no-op, but there is still no RAS DES state to tear down.

So the patch makes the deinit path match the init path: if no
rasdes_info was allocated, skip the RAS DES mutex teardown.

Thanks,
Shuvam