linux-kernel - Re: [PATCH 07/21] ata: libahci_platform: Sanity check the DT child nodes number

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Message-ID: <a2597470-8998-92a4-8085-0503974ce237@opensource.wdc.com>
Date:   Thu, 24 Mar 2022 17:13:45 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Sergey Shtylyov <s.shtylyov@....ru>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Rob Herring <robh+dt@...nel.org>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 07/21] ata: libahci_platform: Sanity check the DT child
 nodes number

On 3/24/22 17:12, Sergey Shtylyov wrote:
> On 3/24/22 4:40 AM, Damien Le Moal wrote:
> 
>>> Having greater than (AHCI_MAX_PORTS = 32) ports detected isn't that
>>> critical from the further AHCI-platform initialization point of view since
>>> exceeding the ports upper limit will cause allocating more resources than
>>> will be used afterwards. But detecting too many child DT-nodes doesn't
>>> seem right since it's very unlikely to have it on an ordinary platform. In
>>> accordance with the AHCI specification there can't be more than 32 ports
>>> implemented at least due to having the CAP.NP field of 4 bits wide and the
>>> PI register of dword size. Thus if such situation is found the DTB must
>>> have been corrupted and the data read from it shouldn't be reliable. Let's
>>> consider that as an erroneous situation and halt further resources
>>> allocation.
>>>
>>> Note it's logically more correct to have the nports set only after the
>>> initialization value is checked for being sane. So while at it let's make
>>> sure nports is assigned with a correct value.
>>>
>>> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
>>> ---
>>>  drivers/ata/libahci_platform.c | 16 +++++++++++-----
>>>  1 file changed, 11 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
>>> index 4fb9629c03ab..845042295b97 100644
>>> --- a/drivers/ata/libahci_platform.c
>>> +++ b/drivers/ata/libahci_platform.c
>>> @@ -470,15 +470,21 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>>>  		}
>>>  	}
>>>  
>>> -	hpriv->nports = child_nodes = of_get_child_count(dev->of_node);
>>> -
>>>  	/*
>>> -	 * If no sub-node was found, we still need to set nports to
>>> -	 * one in order to be able to use the
>>> +	 * Too many sub-nodes most likely means having something wrong with
>>> +	 * firmware. If no sub-node was found, we still need to set nports
>>> +	 * to one in order to be able to use the
>>>  	 * ahci_platform_[en|dis]able_[phys|regulators] functions.
>>>  	 */
>>> -	if (!child_nodes)
>>> +	child_nodes = of_get_child_count(dev->of_node);
>>> +	if (child_nodes > AHCI_MAX_PORTS) {
>>> +		rc = -EINVAL;
>>> +		goto err_out;
>>> +	} else if (!child_nodes) {
>>
>> No need for "else" after a return.
> 
>    You meant *goto*? :-)

Yes :) No need for the else after goto.

> 
> [...]
> 
> MBR, Sergey


-- 
Damien Le Moal
Western Digital Research