[PATCH 2/3 V3] kvm tools: Prevent PFN wraparound

levinsasha928
2011-05-11T15:42:05Z

From: Sasha Levin <levinsasha928@gmail.com>

queue->pfn may be used to point at addresses larger
than 32 bit.
Prevent a wraparound when shifting it left.

Changes in V2:
- Use helper function.

Changes in V3:
- Add warning for using guest_pfn_to_host() on 32-bit hosts.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
tools/kvm/include/kvm/virtio.h | 10 ++++++++++
tools/kvm/virtio/blk.c | 2 +-
tools/kvm/virtio/console.c | 2 +-
tools/kvm/virtio/net.c | 2 +-
tools/kvm/virtio/rng.c | 2 +-
5 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/tools/kvm/include/kvm/virtio.h b/tools/kvm/include/kvm/virtio.h
index 7f92dea..bea63df 100644
--- a/tools/kvm/include/kvm/virtio.h
+++ b/tools/kvm/include/kvm/virtio.h
@@ -36,6 +36,16 @@ static inline bool virt_queue__available(struct virt_queue *vq)
return vq->vring.avail->idx != vq->last_avail_idx;
}

+/*
+ * Warning: on 32-bit hosts, shifting pfn left may cause a truncation of pfn values
+ * higher than 4GB - thus, pointing to the wrong area in guest virtual memory space
+ * and breaking the virt queue which owns this pfn.
+ */
+static inline void *guest_pfn_to_host(struct kvm *kvm, u32 pfn)
+{
+ return guest_flat_to_host(kvm, (unsigned long)pfn << 12);
+}
+
struct vring_used_elem *virt_queue__set_used_elem(struct virt_queue *queue, u32 head, u32 len);

u16 virt_queue__get_iov(struct virt_queue *queue, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm);
diff --git a/tools/kvm/virtio/blk.c b/tools/kvm/virtio/blk.c
index 12c7029..9f1aa1d 100644
--- a/tools/kvm/virtio/blk.c
+++ b/tools/kvm/virtio/blk.c
@@ -197,7 +197,7 @@ static bool virtio_blk_pci_io_out(struct kvm *self, u16 port, void *data, int si

queue = &bdev->vqs[bdev->queue_selector];
queue->pfn = ioport__read32(data);
- p = guest_flat_to_host(self, queue->pfn << 12);
+ p = guest_pfn_to_host(self, queue->pfn);

vring_init(&queue->vring, VIRTIO_BLK_QUEUE_SIZE, p, 4096);

diff --git a/tools/kvm/virtio/console.c b/tools/kvm/virtio/console.c
index f9031cb..87b816a 100644
--- a/tools/kvm/virtio/console.c
+++ b/tools/kvm/virtio/console.c
@@ -199,7 +199,7 @@ static bool virtio_console_pci_io_out(struct kvm *self, u16 port, void *data, in

queue = &cdev.vqs[cdev.queue_selector];
queue->pfn = ioport__read32(data);
- p = guest_flat_to_host(self, queue->pfn << 12);
+ p = guest_pfn_to_host(self, queue->pfn);

vring_init(&queue->vring, VIRTIO_CONSOLE_QUEUE_SIZE, p, 4096);

diff --git a/tools/kvm/virtio/net.c b/tools/kvm/virtio/net.c
index 8d430e3..3f3ee22 100644
--- a/tools/kvm/virtio/net.c
+++ b/tools/kvm/virtio/net.c
@@ -245,7 +245,7 @@ static bool virtio_net_pci_io_out(struct kvm *self, u16 port, void *data, int si

queue = &net_device.vqs[net_device.queue_selector];
queue->pfn = ioport__read32(data);
- p = guest_flat_to_host(self, queue->pfn << 12);
+ p = guest_pfn_to_host(self, queue->pfn);

vring_init(&queue->vring, VIRTIO_NET_QUEUE_SIZE, p, 4096);

diff --git a/tools/kvm/virtio/rng.c b/tools/kvm/virtio/rng.c
index f692dfd..1951d0d1c 100644
--- a/tools/kvm/virtio/rng.c
+++ b/tools/kvm/virtio/rng.c
@@ -129,7 +129,7 @@ static bool virtio_rng_pci_io_out(struct kvm *kvm, u16 port, void *data, int siz

queue = &rdev.vqs[rdev.queue_selector];
queue->pfn = ioport__read32(data);
- p = guest_flat_to_host(kvm, queue->pfn << 12);
+ p = guest_pfn_to_host(kvm, queue->pfn);

vring_init(&queue->vring, VIRTIO_RNG_QUEUE_SIZE, p, 4096);

--
1.7.5.rc3