linux-kernel - Re: [PATCH v2] nvdimm: Avoid race between probe and reading device attributes

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Date:   Mon, 15 Jun 2020 16:36:17 +0800
From:   Coly Li <colyli@...e.de>
To:     Richard Palethorpe <rpalethorpe@...e.com>,
        linux-nvdimm@...ts.01.org
Cc:     linux-kernel@...r.kernel.org, Coly Li <colyli@...e.com>
Subject: Re: [PATCH v2] nvdimm: Avoid race between probe and reading device
 attributes

On 2020/6/15 15:47, Richard Palethorpe wrote:
> It is possible to cause a division error and use-after-free by querying the
> nmem device before the driver data is fully initialised in nvdimm_probe. E.g
> by doing
> 
> (while true; do
>      cat /sys/bus/nd/devices/nmem*/available_slots 2>&1 > /dev/null
>  done) &
> 
> while true; do
>      for i in $(seq 0 4); do
> 	 echo nmem$i > /sys/bus/nd/drivers/nvdimm/bind
>      done
>      for i in $(seq 0 4); do
> 	 echo nmem$i > /sys/bus/nd/drivers/nvdimm/unbind
>      done
>  done
> 
> On 5.7-rc3 this causes:

[snipped]

> 
> This can be prevented by setting the driver data after initialisation is
> complete.
> 
> Fixes: 4d88a97aa9e8 ("libnvdimm, nvdimm: dimm driver and base libnvdimm device-driver infrastructure")
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: linux-nvdimm@...ts.01.org
> Cc: linux-kernel@...r.kernel.org
> Cc: Coly Li <colyli@...e.com>
> Signed-off-by: Richard Palethorpe <rpalethorpe@...e.com>


Reviewed-by: Coly Li <colyli@...e.de>

Thanks.

Coly Li

> ---
> 
> V2:
> + Reviewed by Coly and removed unecessary lock
> 
>  drivers/nvdimm/dimm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvdimm/dimm.c b/drivers/nvdimm/dimm.c
> index 7d4ddc4d9322..3d3988e1d9a0 100644
> --- a/drivers/nvdimm/dimm.c
> +++ b/drivers/nvdimm/dimm.c
> @@ -43,7 +43,6 @@ static int nvdimm_probe(struct device *dev)
>  	if (!ndd)
>  		return -ENOMEM;
>  
> -	dev_set_drvdata(dev, ndd);
>  	ndd->dpa.name = dev_name(dev);
>  	ndd->ns_current = -1;
>  	ndd->ns_next = -1;
> @@ -106,6 +105,8 @@ static int nvdimm_probe(struct device *dev)
>  	if (rc)
>  		goto err;
>  
> +	dev_set_drvdata(dev, ndd);
> +
>  	return 0;
>  
>   err:
>