vfio/pci: Fix OpRegion read

This is to fix incorrect pointer arithmetic which caused wrong
OpRegion version returned, then VM driver got error to get wanted
VBT block. We need to be safe to return correct data, so force
pointer type for byte access.

Fixes: 49ba1a2 ("vfio/pci: Add OpRegion 2.0+ Extended VBT support.")
Cc: Colin Xu <[email protected]>
Cc: Alex Williamson <[email protected]>
Cc: Dmitry Torokhov <[email protected]>
Cc: "Xu, Terrence" <[email protected]>
Cc: "Gao, Fred" <[email protected]>
Acked-by: Colin Xu <[email protected]>
Signed-off-by: Zhenyu Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[aw: line wrap]
Signed-off-by: Alex Williamson <[email protected]>

Author: zhenyw

drivers/vfio/pci/vfio_pci_igd.c

@@ -98,7 +98,8 @@ static ssize_t vfio_pci_igd_rw(struct vfio_pci_core_device *vdev,
 			version = cpu_to_le16(0x0201);
 
 		if (igd_opregion_shift_copy(buf, &off,
-					    &version + (pos - OPREGION_VERSION),
+					    (u8 *)&version +
+					    (pos - OPREGION_VERSION),
 					    &pos, &remaining, bytes))
 			return -EFAULT;
 	}
@@ -121,7 +122,7 @@ static ssize_t vfio_pci_igd_rw(struct vfio_pci_core_device *vdev,
 					  OPREGION_SIZE : 0);
 
 		if (igd_opregion_shift_copy(buf, &off,
-					    &rvda + (pos - OPREGION_RVDA),
+					    (u8 *)&rvda + (pos - OPREGION_RVDA),
 					    &pos, &remaining, bytes))
 			return -EFAULT;
 	}