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

From: Shuvam Pandey <shuvampandey1@gmail.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "Jingoo Han" <jingoohan1@gmail.com>,
	"Manivannan Sadhasivam" <mani@kernel.org>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Yue Wang" <yue.wang@amlogic.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Rob Herring" <robh@kernel.org>,
	"Kevin Hilman" <khilman@baylibre.com>,
	"Jerome Brunet" <jbrunet@baylibre.com>,
	"Martin Blumenstingl" <martin.blumenstingl@googlemail.com>,
	"Fan Ni" <fan.ni@samsung.com>,
	"Shradha Todi" <shradha.t@samsung.com>,
	"Hanjie Lin" <hanjie.lin@amlogic.com>,
	linux-pci@vger.kernel.org, linux-amlogic@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] PCI: dwc: Guard RAS DES debugfs deinit
Date: Fri, 12 Jun 2026 20:38:41 +0545	[thread overview]
Message-ID: <CANAAWHKBFmgQfqUNaiUrPxBk4bPoBpRbhJs9YqszKvBUbUrMXg@mail.gmail.com> (raw)
In-Reply-To: <20260611221000.GA524832@bhelgaas>

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

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