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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Fri, 9 Apr 2021 21:54:50 -0700
Message-ID: <CAPcyv4hBN2eCGehzZES7_NNco5xupKsvv69JtxzzCoV-DzT9bQ@mail.gmail.com>
Subject: Re: [PATCH v1] libnvdimm, dax: Fix a missing check in nd_dax_probe()
To:     wangyingjie55@126.com
Cc:     Vishal L Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        "Weiny, Ira" <ira.weiny@intel.com>,
        linux-nvdimm <linux-nvdimm@lists.01.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Fri, Apr 9, 2021 at 5:33 PM <wangyingjie55@126.com> wrote:
>
> From: Yingjie Wang <wangyingjie55@126.com>
>
> In nd_dax_probe(), 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@126.com>
> ---
>  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);

hmmm...

>         nd_dax = nd_dax_alloc(nd_region);
> +       if (!nd_dax)
> +               return -ENOMEM;

Can you spot the bug this introduces? See the hint above.

>         nd_pfn = &nd_dax->nd_pfn;
>         dax_dev = nd_pfn_devinit(nd_pfn, ndns);
>         nvdimm_bus_unlock(&ndns->dev);
> --
> 2.7.4
>