Re: [PATCH V2 1/1] device-dax: check for vma range while dax_mmap.

[Dave Jiang]

On 08/20/2018 10:53 AM, Verma, Vishal L wrote:
> 
> On Mon, 2018-08-13 at 20:02 +0800, Zhang Yi wrote:
>> This patch prevents a user mapping an illegal vma range that is larger
>> than a dax device physical resource.
>>
>> When qemu maps the dax device for virtual nvdimm's backend device, the
>> v-nvdimm label area is defined at the end of mapped range. By using an
>> illegal size that exceeds the range of the device dax, it will trigger a
>> fault with qemu.
>>
>> Signed-off-by: Zhang Yi <yi.z.zhang@xxxxxxxxxxxxxxx>
>> ---
>>  drivers/dax/device.c | 29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
> 
> Looks good to me:
> Reviewed-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>

Applied.

> 
>> diff --git a/drivers/dax/device.c b/drivers/dax/device.c
>> index 108c37f..6fe8c30 100644
>> --- a/drivers/dax/device.c
>> +++ b/drivers/dax/device.c
>> @@ -177,6 +177,33 @@ static const struct attribute_group *dax_attribute_groups[] = {
>>  	NULL,
>>  };
>>  
>> +static int check_vma_range(struct dev_dax *dev_dax, struct vm_area_struct *vma,
>> +		const char *func)
>> +{
>> +	struct device *dev = &dev_dax->dev;
>> +	struct resource *res;
>> +	unsigned long size;
>> +	int ret, i;
>> +
>> +	if (!dax_alive(dev_dax->dax_dev))
>> +		return -ENXIO;
>> +
>> +	size = vma->vm_end - vma->vm_start + (vma->vm_pgoff << PAGE_SHIFT);
>> +	ret = -EINVAL;
>> +	for (i = 0; i < dev_dax->num_resources; i++) {
>> +		res = &dev_dax->res[i];
>> +		if (size > resource_size(res)) {
>> +			dev_info_ratelimited(dev,
>> +				"%s: %s: fail, vma range overflow\n",
>> +				current->comm, func);
>> +			ret = -EINVAL;
>> +			continue;
>> +		} else
>> +			return 0;
>> +	}
>> +	return ret;
>> +}
>> +
>>  static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
>>  		const char *func)
>>  {
>> @@ -469,6 +496,8 @@ static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
>>  	 */
>>  	id = dax_read_lock();
>>  	rc = check_vma(dev_dax, vma, __func__);
>> +	if (!rc)
>> +		rc = check_vma_range(dev_dax, vma, __func__);
>>  	dax_read_unlock(id);
>>  	if (rc)
>>  		return rc;