Re: [PATCH -next] PCI: dra7xx: Fix potential NULL dereference

From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Ladislav Michl <ladis@linux-mips.org>,
	Wei Yongjun <weiyongjun1@huawei.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
	Kishon Vijay Abraham I <kishon@ti.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-omap@vger.kernel.org, linux-pci@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: Re: [PATCH -next] PCI: dra7xx: Fix potential NULL dereference
Date: Fri, 16 Nov 2018 11:51:29 +0000	[thread overview]
Message-ID: <20181116115129.GA3228@e107981-ln.cambridge.arm.com> (raw)
In-Reply-To: <20180120001645.GA21343@lenoch>

On Sat, Jan 20, 2018 at 01:16:45AM +0100, Ladislav Michl wrote:
> On Fri, Jan 19, 2018 at 06:06:57PM +0100, Ladislav Michl wrote:
> > On Fri, Jan 19, 2018 at 10:58:57AM +0100, Ladislav Michl wrote:
> > > On Thu, Jan 18, 2018 at 12:35:25PM -0600, Bjorn Helgaas wrote:
> > > > That's probably a better idea.  Maybe we should add a comment like this
> > > > to help avoid this in the future:
> > > 
> > > That seems to spot another a bit more serious problem (given how late
> > > release cycle is now).
> > > 
> > > Both devm_ioremap() and devm_ioremap_resource() shares the same release
> > > function: devm_ioremap_release(). However this function is not aware of
> > > memory region previously requested by devm_request_mem_region() called
> > > from devm_ioremap_resource().
> > > 
> > > Bellow is just a quick hack, even untested as looking at devm_ioremap,
> > > devm_ioremap_wc and devm_ioremap_wc, there is some room for optimization.
> > 
> > Okay, forget it, above analysis is not correct, however there is a bug (and
> > also in PCI version). To show it, let's make following modification:
> 
> I will never ever work in single tree for two different boards without full
> recompile (which should save time and caused opposite) as it makes debugging
> pointless - there is no bug.
> 
> As a request forgiveness, please accept following draft as proposed solution
> for $subj

Wei, Ladislav,

getting back to this old thread, I would mark it as "changes requested"
and expect someone to post a follow-up patch, I do not think this is
a solved problem.

Lorenzo

> Subject: [PATCH] PCI: dra7xx: Use devm_ioremap_resource()
> 
> diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c
> index 8bf7c2714db6..7f422ae258ac 100644
> --- a/drivers/pci/dwc/pci-dra7xx.c
> +++ b/drivers/pci/dwc/pci-dra7xx.c
> @@ -409,14 +409,14 @@ static int __init dra7xx_add_pcie_ep(struct dra7xx_pcie *dra7xx,
>  	ep->ops = &pcie_ep_ops;
>  
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "ep_dbics");
> -	pci->dbi_base = devm_ioremap(dev, res->start, resource_size(res));
> -	if (!pci->dbi_base)
> -		return -ENOMEM;
> +	pci->dbi_base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(pci->dbi_base))
> +		return PTR_ERR(pci->dbi_base);
>  
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "ep_dbics2");
> -	pci->dbi_base2 = devm_ioremap(dev, res->start, resource_size(res));
> -	if (!pci->dbi_base2)
> -		return -ENOMEM;
> +	pci->dbi_base2 = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(pci->dbi_base2))
> +		return PTR_ERR(pci->dbi_base2);
>  
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "addr_space");
>  	if (!res)