linux-kernel - Re: [PATCH v5 13/16] cxl/pci: Add error handler for CXL PCIe Port RAS errors

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Message-ID: <dca3416c-4827-4dd5-93f2-023a05037e5f@amd.com>
Date: Fri, 7 Feb 2025 15:04:20 -0600
From: "Bowman, Terry" <terry.bowman@....com>
To: Gregory Price <gourry@...rry.net>
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pci@...r.kernel.org, nifan.cxl@...il.com, dave@...olabs.net,
 jonathan.cameron@...wei.com, dave.jiang@...el.com,
 alison.schofield@...el.com, vishal.l.verma@...el.com,
 dan.j.williams@...el.com, bhelgaas@...gle.com, mahesh@...ux.ibm.com,
 ira.weiny@...el.com, oohall@...il.com, Benjamin.Cheatham@....com,
 rrichter@....com, nathan.fontenot@....com,
 Smita.KoralahalliChannabasappa@....com, lukas@...ner.de,
 ming.li@...omail.com, PradeepVineshReddy.Kodamati@....com, alucerop@....com
Subject: Re: [PATCH v5 13/16] cxl/pci: Add error handler for CXL PCIe Port RAS
 errors



On 2/7/2025 1:41 PM, Gregory Price wrote:
> On Fri, Feb 07, 2025 at 01:23:06PM -0600, Bowman, Terry wrote:
>>
>> On 2/7/2025 2:01 AM, Gregory Price wrote:
>>> On Tue, Jan 07, 2025 at 08:38:49AM -0600, Terry Bowman wrote:
>>>> +static void __iomem *cxl_pci_port_ras(struct pci_dev *pdev)
>>>> +{
>>>> +	struct cxl_port *port;
>>>> +
>>>> +	if (!pdev)
>>>> +		return NULL;
>>>> +
>>>> +	if ((pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT) ||
>>>> +	    (pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM)) {
>>>> +		struct cxl_dport *dport;
>>>> +		void __iomem *ras_base;
>>>> +
>>>> +		port = find_cxl_port(&pdev->dev, &dport);
>>>> +		ras_base = dport ? dport->regs.ras : NULL;
>>> I'm fairly certain dport can come back here uninitialized, you
>>> probably want to put this inside the `if (port)` block and 
>>> pre-initialize dport to NULL.
>> Right, it can. NULL dport check here covers this, no?:
>>
>> 		ras_base = dport ? dport->regs.ras : NULL;
> dport can be garbage (whatever is on the stack) at this check because
> nothing ever intializes it to NULL.

Got it. Thanks.
>> Terry
>>
>>>> +		if (port)
>>>> +			put_device(&port->dev);
>>>> +		return ras_base;
>>> You can probably even simplify this down to something like
>>>
>>> 		struct_cxl_dport *dport = NULL;
>>>
>>> 		port = find_cxl_port(&pdev->dev, &dport);
>>> 		if (port)
>>> 			put_device(&port->dev);
>>>
>>> 		return dport ? dport->regs.ras : NULL;
>>>
>>>
>>> ~Gregory