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SubjectRe: [RFC PATCH 1/1] device-dax: check for vma range while dax_mmap.
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On 2018年08月02日 03:40, Dave Jiang wrote:
>
> On 07/31/2018 04:46 AM, Zhang Yi wrote:
>> It should be prevent user map an illegal vma range which larger than
>> dax device phiscal resourse, as we don't have swap logic while page
>> faulting in dax device.
> This patch prevents a user mapping an illegal vma range that is larger
> than a dax device physical resource.
>
>> Applications, especailly qemu, map the /dev/dax for virtual nvdimm's
>> backend device, we defined the v-nvdimm label area at the end of mapped
>> rang. By using an illegal size that exceeds the physical resource of
>> /dev/dax, then it will triger qemu a signal fault while accessing these
>> label area.
> 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.
Thanks Dava, that's could be much better.
>
>> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
>> ---
>> drivers/dax/device.c | 28 ++++++++++++++++++++++++++++
>> 1 file changed, 28 insertions(+)
>>
>> diff --git a/drivers/dax/device.c b/drivers/dax/device.c
>> index aff2c15..c9a50cd 100644
>> --- a/drivers/dax/device.c
>> +++ b/drivers/dax/device.c
>> @@ -177,6 +177,32 @@ 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(dev, "%s: %s: fail, vma range is 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)
>> {
>> @@ -465,6 +491,8 @@ 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__);
> I think you want to augment check_vma() rather than adding another
> function? If this is added inside check_vma() then you can also skip the
> !dax_alive() check. Do you expect this function to be called anywhere else?
since check_vma range also will be called while dax page faulting. I
don't wanna this check_vma_range introduce some additional workload
while page fault. just let it checked in the mmap scenario
>
>> dax_read_unlock(id);
>> if (rc)
>> return rc;
>>

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