linux-kernel - Re: [PATCH v1] libnvdimm, dax: Fix a missing check in nd_dax

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Date:   Fri, 9 Apr 2021 09:41:45 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     wangyingjie55@....com
Cc:     dan.j.williams@...el.com, vishal.l.verma@...el.com,
        dave.jiang@...el.com, linux-nvdimm@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] libnvdimm, dax: Fix a missing check in nd_dax_probe()

On Thu, Apr 08, 2021 at 06:58:26PM -0700, wangyingjie55@....com wrote:
> From: Yingjie Wang <wangyingjie55@....com>
> 
> In nd_dax_probe(), 'nd_dax' is allocated by nd_dax_alloc().
> nd_dax_alloc() may fail and return NULL, so we should better check

Avoid the use of 'we'.

> it's return value to avoid a NULL pointer dereference
> a bit later in the code.

How about:

"nd_dax_alloc() may fail and return NULL.  Check for NULL before attempting to
use nd_dax to avoid a NULL pointer dereference."

> 
> Fixes: c5ed9268643c ("libnvdimm, dax: autodetect support")
> Signed-off-by: Yingjie Wang <wangyingjie55@....com>

The code looks good though.

Ira

> ---
>  drivers/nvdimm/dax_devs.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/nvdimm/dax_devs.c b/drivers/nvdimm/dax_devs.c
> index 99965077bac4..b1426ac03f01 100644
> --- a/drivers/nvdimm/dax_devs.c
> +++ b/drivers/nvdimm/dax_devs.c
> @@ -106,6 +106,8 @@ int nd_dax_probe(struct device *dev, struct nd_namespace_common *ndns)
>  
>  	nvdimm_bus_lock(&ndns->dev);
>  	nd_dax = nd_dax_alloc(nd_region);
> +	if (!nd_dax)
> +		return -ENOMEM;
>  	nd_pfn = &nd_dax->nd_pfn;
>  	dax_dev = nd_pfn_devinit(nd_pfn, ndns);
>  	nvdimm_bus_unlock(&ndns->dev);
> -- 
> 2.7.4
>