[SLOF] [PATCH 1/3] virtio-serial: Fix invalid stack access with closed virtio device

[Jordan Niethe]

When virtiodev is 0, its read method accesses beyond the end of the
stack with nip.  Instead finish with 1 on the stack to mirror the
virtio-serial-getchar case and the behavior of the write method to
return successfully even with the virtio device closed.

Fixes: 8174acd ("virtio-serial: Close device completely")
Co-developed-by: Kautuk Consul <kconsul at linux.vnet.ibm.com>
Signed-off-by: Kautuk Consul <kconsul at linux.vnet.ibm.com>
Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
---
 board-qemu/slof/virtio-serial.fs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/board-qemu/slof/virtio-serial.fs b/board-qemu/slof/virtio-serial.fs
index 82868e2..a67a310 100644
--- a/board-qemu/slof/virtio-serial.fs
+++ b/board-qemu/slof/virtio-serial.fs
@@ -78,7 +78,7 @@ virtiodev virtio-serial-init drop
 
 : read ( addr len -- actual )
     0= IF drop 0 EXIT THEN
-    virtiodev 0= IF nip EXIT THEN
+    virtiodev 0= IF drop 1 EXIT THEN
     virtiodev virtio-serial-haschar 0= IF 0 swap c! -2 EXIT THEN
     virtiodev virtio-serial-getchar swap c! 1
 ;
-- 
2.39.3