[PATCH 5.7 167/204] vdpa: Fix pointer math bug in vdpasim_get_config()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit cf16fe9243bfa2863491026fc727618c7c593c84 ]

If "offset" is non-zero then we end up copying from beyond the end of
the config because of pointer math.  We can fix this by casting the
struct to a u8 pointer.

Fixes: 2c53d0f64c06 ("vdpasim: vDPA device simulator")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200406144552.GF68494@mwanda
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 3554f8de00e64..4907c1cfe6671 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -521,7 +521,7 @@ static void vdpasim_get_config(struct vdpa_device *vdpa, unsigned int offset,
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
 	if (offset + len < sizeof(struct virtio_net_config))
-		memcpy(buf, &vdpasim->config + offset, len);
+		memcpy(buf, (u8 *)&vdpasim->config + offset, len);
 }
 
 static void vdpasim_set_config(struct vdpa_device *vdpa, unsigned int offset,
-- 
2.25.1