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Message-ID: <f0a15a0d-7cb3-f635-d8d6-6c32e83ed93b@suse.de>
Date:   Thu, 12 May 2022 08:34:04 +0200
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Subject: Re: [PATCH v3 09/23] ata: libahci_platform: Sanity check the DT child
 nodes number
Content-Language: en-US
To:     Serge Semin <Sergey.Semin@baikalelectronics.ru>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Jens Axboe <axboe@kernel.dk>
Cc:     Serge Semin <fancer.lancer@gmail.com>,
        Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>,
        Rob Herring <robh+dt@kernel.org>, linux-ide@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
References: <20220511231810.4928-1-Sergey.Semin@baikalelectronics.ru>
 <20220511231810.4928-10-Sergey.Semin@baikalelectronics.ru>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <20220511231810.4928-10-Sergey.Semin@baikalelectronics.ru>
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On 5/12/22 01:17, Serge Semin 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@baikalelectronics.ru>
> 
> ---
> 
> Changelog v2:
> - Drop the else word from the child_nodes value checking if-else-if
>    statement (@Damien) and convert the after-else part into the ternary
>    operator-based statement.
> ---
>   drivers/ata/libahci_platform.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
> index 7ff6626fd569..4e54e19f07b2 100644
> --- a/drivers/ata/libahci_platform.c
> +++ b/drivers/ata/libahci_platform.c
> @@ -480,15 +480,22 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
>   		}
>   	}
>   
> -	hpriv->nports = child_nodes = of_get_child_count(dev->of_node);
> +	/*
> +	 * Too many sub-nodes most likely means having something wrong with
> +	 * the firmware.
> +	 */
> +	child_nodes = of_get_child_count(dev->of_node);
> +	if (child_nodes > AHCI_MAX_PORTS) {
> +		rc = -EINVAL;
> +		goto err_out;
> +	}
>   
>   	/*
>   	 * 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)
> -		hpriv->nports = 1;
> +	hpriv->nports = child_nodes ?: 1;
>   
>   	hpriv->phys = devm_kcalloc(dev, hpriv->nports, sizeof(*hpriv->phys), GFP_KERNEL);
>   	if (!hpriv->phys) {

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer