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

Commit Message

Sasha Levin May 11, 2011, 3:17 p.m. UTC

From: Sasha Levin <[e-mail]>

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 <[e-mail]>
---
 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(-)

Patch

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);