linux-kernel - Re: [PATCH v3] ide: Check for null pointer after calling devm

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Message-ID: <177f3741-ca31-b5ac-69ff-1adf346f1199@opensource.wdc.com>
Date:   Sat, 8 Jan 2022 11:53:42 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>, David.Laight@...LAB.COM,
        davem@...emloft.net,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] ide: Check for null pointer after calling devm_ioremap

On 2022/01/07 21:53, Jiasheng Jiang wrote:
> In linux-stable-5.15.13, this file has been removed and combined
> to `drivers/ata/pata_platform.c` without this bug.
> But in the older LTS kernels, like 5.10.90, this bug still exists.
> 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' are 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.
> Actually, it introduced the bug from commit 8cb1f567f4c0
> ("ide: Platform IDE driver") and we can know from the commit message
> that it tended to be similar to the `drivers/ata/pata_platform.c`.
> But actually, even the first time pata_platform was built,
> commit a20c9e820864 ("[PATCH] ata: Generic platform_device libata driver"),
> there was no the bug, as there was a check after the ioremap().
> So possibly the bug was caused by ide itself.
> 
> Fixes: 8cb1f567f4c0 ("ide: Platform IDE driver")
> Cc: stable@...r.kernel.org#5.10

Please keep the space before the #

Cc: stable@...r.kernel.org #5.10

> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog
> 
> v1 -> v2
> 
> * Change 1. Correct the fixes tag and commit message.
> 
> v2 -> v3
> 
> * Change 1. Correct the code.

As commented before, what exactly was corrected ? That is what needs to be
mentioned here. In any case, I fail to see what code change you added between v2
and v3. The code changes are identical in the 2 versions.

> ---
>  drivers/ide/ide_platform.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/ide/ide_platform.c b/drivers/ide/ide_platform.c
> index 91639fd6c276..5500c5afb3ca 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);

Greg,

The above patch is OK but cannot be applied in the current kernel:
* The Legacy IDE drivers were removed in 5.14, replaced by the already existing
* The current equivalent libata driver (drivers/ata/pata_platform.c) already has
the above error check.

So I think this patch needs to go directly to stable # 5.10 and earlier LTS
kernels. Can you take it ?

Feel free to add:

Acked-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>

Note that I was not the maintainer of the IDE drivers. If more appropriate
please feel free to replace that with a Reviewed-by tag.

Thanks !

-- 
Damien Le Moal
Western Digital Research