On 22/07/2019 15:55, Eric Auger wrote:
> Do not call dma_max_mapping_size for devices that have no DMA
> mask set, otherwise we can hit a NULL pointer dereference.
>
> This occurs when a virtio-blk-pci device is protected with
> a virtual IOMMU.
>
> Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()")
> Signed-off-by: Eric Auger <[email protected]>
> Suggested-by: Christoph Hellwig <[email protected]>
> ---
> drivers/virtio/virtio_ring.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index c8be1c4f5b55..37c143971211 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -262,7 +262,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
> {
> size_t max_segment_size = SIZE_MAX;
>
> - if (vring_use_dma_api(vdev))
> + if (vring_use_dma_api(vdev) && vdev->dev.dma_mask)
Hmm, might it make sense to roll that check up into vring_use_dma_api()
itself? After all, if the device has no mask then it's likely that other
DMA API ops wouldn't really work as expected either.
Robin.
> max_segment_size = dma_max_mapping_size(&vdev->dev);
>
> return max_segment_size;
>
On Mon, Jul 22, 2019 at 04:36:09PM +0100, Robin Murphy wrote:
> On 22/07/2019 15:55, Eric Auger wrote:
> > Do not call dma_max_mapping_size for devices that have no DMA
> > mask set, otherwise we can hit a NULL pointer dereference.
> >
> > This occurs when a virtio-blk-pci device is protected with
> > a virtual IOMMU.
> >
> > Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()")
> > Signed-off-by: Eric Auger <[email protected]>
> > Suggested-by: Christoph Hellwig <[email protected]>
> > ---
> > drivers/virtio/virtio_ring.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index c8be1c4f5b55..37c143971211 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -262,7 +262,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
> > {
> > size_t max_segment_size = SIZE_MAX;
> > - if (vring_use_dma_api(vdev))
> > + if (vring_use_dma_api(vdev) && vdev->dev.dma_mask)
>
> Hmm, might it make sense to roll that check up into vring_use_dma_api()
> itself? After all, if the device has no mask then it's likely that other DMA
> API ops wouldn't really work as expected either.
>
> Robin.
Nope, Eric pointed out it's just dma_addressing_limited that is broken.
Other APIs call dma_get_mask which handles the NULL mask case fine.
> > max_segment_size = dma_max_mapping_size(&vdev->dev);
> > return max_segment_size;
> >
On Mon, Jul 22, 2019 at 04:36:09PM +0100, Robin Murphy wrote:
>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
>> index c8be1c4f5b55..37c143971211 100644
>> --- a/drivers/virtio/virtio_ring.c
>> +++ b/drivers/virtio/virtio_ring.c
>> @@ -262,7 +262,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
>> {
>> size_t max_segment_size = SIZE_MAX;
>> - if (vring_use_dma_api(vdev))
>> + if (vring_use_dma_api(vdev) && vdev->dev.dma_mask)
>
> Hmm, might it make sense to roll that check up into vring_use_dma_api()
> itself? After all, if the device has no mask then it's likely that other
> DMA API ops wouldn't really work as expected either.
Makes sense to me.
On Tue, Jul 23, 2019 at 05:38:51PM +0200, Christoph Hellwig wrote:
> On Mon, Jul 22, 2019 at 04:36:09PM +0100, Robin Murphy wrote:
> >> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> >> index c8be1c4f5b55..37c143971211 100644
> >> --- a/drivers/virtio/virtio_ring.c
> >> +++ b/drivers/virtio/virtio_ring.c
> >> @@ -262,7 +262,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
> >> {
> >> size_t max_segment_size = SIZE_MAX;
> >> - if (vring_use_dma_api(vdev))
> >> + if (vring_use_dma_api(vdev) && vdev->dev.dma_mask)
> >
> > Hmm, might it make sense to roll that check up into vring_use_dma_api()
> > itself? After all, if the device has no mask then it's likely that other
> > DMA API ops wouldn't really work as expected either.
>
> Makes sense to me.
Christoph - would a documented API wrapping dma_mask make sense?
With the documentation explaining how users must
desist from using DMA APIs if that returns false ...
--
MST
Hi,
On 7/23/19 5:38 PM, Christoph Hellwig wrote:
> On Mon, Jul 22, 2019 at 04:36:09PM +0100, Robin Murphy wrote:
>>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
>>> index c8be1c4f5b55..37c143971211 100644
>>> --- a/drivers/virtio/virtio_ring.c
>>> +++ b/drivers/virtio/virtio_ring.c
>>> @@ -262,7 +262,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
>>> {
>>> size_t max_segment_size = SIZE_MAX;
>>> - if (vring_use_dma_api(vdev))
>>> + if (vring_use_dma_api(vdev) && vdev->dev.dma_mask)
>>
>> Hmm, might it make sense to roll that check up into vring_use_dma_api()
>> itself? After all, if the device has no mask then it's likely that other
>> DMA API ops wouldn't really work as expected either.
>
> Makes sense to me.
>
I am confused: if vring_use_dma_api() returns false if the dma_mask is
unset (ie. vring_use_dma_api() returns false), the virtio-blk-pci device
will not be able to get translated addresses and won't work properly.
The patch above allows the dma api to be used and only influences the
max_segment_size and it works properly.
So is it normal the dma_mask is unset in my case?
Thanks
Eric