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

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Date:   Thu, 24 Mar 2022 11:12:01 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        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 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*? :-)

[...]

MBR, Sergey