vfio-pci: Fix possible integer overflow

The VFIO_DEVICE_SET_IRQS ioctl takes a start and count parameter, both
of which are unsigned.  We attempt to bounds check these, but fail to
account for the case where start is a very large number, allowing
start + count to wrap back into the valid range.  Bounds check both
start and start + count.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 8189cb6..7abc5c8 100644 (file)
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -346,6 +346,7 @@ static long vfio_pci_ioctl(void *device_data,
 
                if (!(hdr.flags & VFIO_IRQ_SET_DATA_NONE)) {
                        size_t size;
+                       int max = vfio_pci_get_irq_count(vdev, hdr.index);
 
                        if (hdr.flags & VFIO_IRQ_SET_DATA_BOOL)
                                size = sizeof(uint8_t);
@@ -355,7 +356,7 @@ static long vfio_pci_ioctl(void *device_data,
                                return -EINVAL;
 
                        if (hdr.argsz - minsz < hdr.count * size ||
-                           hdr.count > vfio_pci_get_irq_count(vdev, hdr.index))
+                           hdr.start >= max || hdr.start + hdr.count > max)
                                return -EINVAL;
 
                        data = memdup_user((void __user *)(arg + minsz),