Re: [PATCH v1] libnvdimm, dax: Fix a missing check in nd_dax_probe()

[Dan Williams]

On Fri, Apr 9, 2021 at 5:33 PM  wrote:
>
> From: Yingjie Wang 
>
> 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 
> ---
>  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(>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 = _dax->nd_pfn;
> dax_dev = nd_pfn_devinit(nd_pfn, ndns);
> nvdimm_bus_unlock(>dev);
> --
> 2.7.4
>

Re: [PATCH v1] libnvdimm, dax: Fix a missing check in nd_dax_probe()

[Ira Weiny]

On Thu, Apr 08, 2021 at 06:58:26PM -0700, wangyingji...@126.com wrote:
> From: Yingjie Wang 
> 
> 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 

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(>dev);
>   nd_dax = nd_dax_alloc(nd_region);
> + if (!nd_dax)
> + return -ENOMEM;
>   nd_pfn = _dax->nd_pfn;
>   dax_dev = nd_pfn_devinit(nd_pfn, ndns);
>   nvdimm_bus_unlock(>dev);
> -- 
> 2.7.4
>