linux-kernel - Re: [PATCH v2] ide: Check for null pointer after calling devm

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Message-ID: <e592bbde-0e74-4f7c-9ffc-6b04b90d12ad@opensource.wdc.com>
Date:   Fri, 7 Jan 2022 16:43:16 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>, davem@...emloft.net
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ide: Check for null pointer after calling devm_ioremap

On 1/7/22 16:04, Jiasheng Jiang wrote:
> As the possible failure of the devres_alloc(), the devm_ioremap() and
> devm_ioport_map() may return NULL pointer.
> And then, the 'base' and 'alt_base' is used in plat_ide_setup_ports().
> Therefore, it should be better to add the check in order to avoid the
> dereference of the NULL pointer.
> 
> Fixes: 2bfba3c444fe ("ide: remove useless subdirs from drivers/ide/")

This patch only renamed files under drivers/ide. I do not think it is
the patch that introduced the problem you are trying to fix.

> Cc: 5.10

Please read
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html?highlight=linux%20stable

> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog
> 
> v1 -> v2
> 
> * Change 1. Add cc.

Adding a CC to the distribution list of the patch does not change the
patch itself, so no need for tagging "v2".

> ---
>  drivers/ide/ide_platform.c | 4 ++++

Again, this file does NOT exist anymore.
The legacy IDE driver was removed from the kernel with version 5.14 by
commit b7fb14d3ac63 ("ide: remove the legacy ide driver"). libata now
implements drivers for legacy PATA/IDE drives. Have you checked first if
your fix is needed there ? If it is, then please send your patch against
the current libata tree. If the fix is needed only in older LTS kernels,
then please make that clear in a cover letter with your patch.

>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/ide/ide_platform.c b/drivers/ide/ide_platform.c
> index 91639fd6c276..8c6e1af7b6eb 100644
> --- a/drivers/ide/ide_platform.c
> +++ b/drivers/ide/ide_platform.c
> @@ -85,6 +85,10 @@ static int plat_ide_probe(struct platform_device *pdev)
>  		alt_base = devm_ioport_map(&pdev->dev,
>  			res_alt->start, resource_size(res_alt));
>  	}
> +	if (!base || !alt_base) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
>  
>  	memset(&hw, 0, sizeof(hw));
>  	plat_ide_setup_ports(&hw, base, alt_base, pdata, res_irq->start);


-- 
Damien Le Moal
Western Digital Research