linux-kernel - Re: [PATCH v2] PCI: dwc: keystone: Fix potential NULL dereference

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Date: Sat, 27 Apr 2024 14:14:59 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: Aleksandr Mishin <amishin@...rgos.ru>, Rob Herring <robh@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Serge Semin <fancer.lancer@...il.com>,
	Niklas Cassel <cassel@...nel.org>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Damien Le Moal <dlemoal@...nel.org>,
	Siddharth Vadapalli <s-vadapalli@...com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH v2] PCI: dwc: keystone: Fix potential NULL dereference

On Thu, Apr 25, 2024 at 03:00:14PM +0200, Alexander Lobakin wrote:
> From: Aleksandr Mishin <amishin@...rgos.ru>
> Date: Thu, 25 Apr 2024 12:21:35 +0300
> 
> > In ks_pcie_setup_rc_app_regs() resource_list_first_type() may return
> > NULL which is later dereferenced. Fix this bug by adding NULL check.
> > 
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Please stop spamming with "potential fixes" made mechanically from
> static analyzer reports without looking into the code flow. These
> patches are mostly incorrect and may hurt.
> Either have a stable repro and then fix the real bug or don't touch
> anything at all.
> 

This patch obviously fixes the potential issue where resource_list_first_type()
may return NULL if the MEM range is not provided in DT.
pci_parse_request_of_pci_ranges() will just emit a warning in that case and this
code path will cause a NULL pointer dereference.

Even though this situation means that the DT is broken, it still makes sense to
have the checks in place.

- Mani

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