Re: [PATCH v1 01/16] virtio: Validate queue pfn for 32bit transports
From: Suzuki K Poulose
Date: Wed Jan 10 2018 - 06:18:20 EST
On 10/01/18 11:06, Michael S. Tsirkin wrote:
On Wed, Jan 10, 2018 at 10:54:09AM +0000, Suzuki K Poulose wrote:
On 09/01/18 23:29, Michael S. Tsirkin wrote:
On Tue, Jan 09, 2018 at 07:03:56PM +0000, Suzuki K Poulose wrote:
virtio-mmio using virtio-v1 and virtio legacy pci use a 32bit PFN
for the queue. If the queue pfn is too large to fit in 32bits, which
we could hit on arm64 systems with 52bit physical addresses (even with
64K page size), we simply miss out a proper link to the other side of
the queue.
Add a check to validate the PFN, rather than silently breaking
the devices.
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <cdall@xxxxxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Could you guys please work on virtio 1 support in
for virtio mmio in qemu though?
It's not a lot of code.
Did you mean kvmtool ? Qemu already supports virto-1.
For virtio-mmio? I don't seem to see that code in
hw/virtio/virtio-mmio.c
For example I still see handling for VIRTIO_MMIO_QUEUE_PFN
there, and no handling for VIRTIO_MMIO_QUEUE_DESC_LOW
and such.
What am I missing?
Nah, you're right. Its the PCI that uses QUEUE_DESC_LOW/HIGH.
Btw, I can't work on Qemu.
---
drivers/virtio/virtio_mmio.c | 19 ++++++++++++++++---
drivers/virtio/virtio_pci_legacy.c | 11 +++++++++--
2 files changed, 25 insertions(+), 5 deletions(-)
I'd rather see this as 2 patches.
OK, I will split them.
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index a9192fe4f345..47109baf37f7 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -358,6 +358,7 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
struct virtqueue *vq;
unsigned long flags;
unsigned int num;
+ u64 addr;
int err;
if (!name)
@@ -394,16 +395,26 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
goto error_new_virtqueue;
}
+ addr = virtqueue_get_desc_addr(vq);
+ /*
+ * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something that
+ * doesn't fit in 32bit, fail the setup rather than pretending to
+ * be successful.
+ */
+ if (vm_dev->version == 1 && (addr >> (PAGE_SHIFT + 32))) {
+ dev_err(&vdev->dev, "virtio-mmio: queue address too large\n");
+ err = -ENOMEM;
+ goto error_bad_pfn;
+ }
+
Can you please move this below to where it's actually used?
The reason for keeping it here was to skip selecting the Queue number if we
have a bad PFN.
Why is selecting a problem if we don't program anything?
I will be honest here, I don't know :-). The only reasoning was why do something
that you are not going to use after all. I will move it down.
May be it doesn't make much difference as we write PFN = 0 anyway
down.
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -122,6 +122,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
struct virtqueue *vq;
u16 num;
int err;
+ u64 q_pfn;
/* Select the queue we're interested in */
iowrite16(index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
@@ -141,9 +142,15 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
if (!vq)
return ERR_PTR(-ENOMEM);
+ q_pfn = virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT;
+ if (q_pfn >> 32) {
+ dev_err(&vp_dev->pci_dev->dev, "virtio-pci queue PFN too large\n");
+ err = -ENOMEM;
+ goto out_deactivate;
You never set up the address, it's cleaner to add another target
and not reset it.
Thats right. However, the only thing we do is writing PFN=0, which would be a good
thing to do to indicate the error to the host ?
It isn't, a good way to indicate error is to set a bad status
which happens anyway I think. Writing PFN 0 resets the device
instead.
Ok, thats good to know. I will make the necessary changes. Thanks for the explanation.
Cheers
Suzuki