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.zh...@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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