virtio-serial: Close device completely

Linux closes stdout at the end of prom_init which triggers the FW quiesce
code which closes the virtio-serial instance. This misses stopping the
virtio queues. However this seemed working for a little longer (until the
Linux driver took over) till 300384f3dc68 which moved the VQ descriptors
around which caused use-after-free corruption.

This adds virtio_queue_term_vq(), cleanup in the forth driver and a few
checks.

Fixes: 300384f3dc68 ("virtio: Store queue descriptors in virtio_device")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[groug: - fix changelog
        - don't restore emit]
Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

1 files changed, 3 insertions, 0 deletions

diff --git a/board-qemu/slof/virtio-serial.fs b/board-qemu/slof/virtio-serial.fs
index e307231..ac55ffc 100644
--- a/board-qemu/slof/virtio-serial.fs
+++ b/board-qemu/slof/virtio-serial.fs
@@ -21,6 +21,7 @@ virtio-setup-vd VALUE virtiodev
 : shutdown  ( -- )
     virtiodev virtio-serial-shutdown
     FALSE to initialized?
+    0 to virtiodev
 ;
 
 : virtio-serial-term-emit
@@ -58,6 +59,7 @@ virtiodev virtio-serial-init drop
 ;
 
 : write ( addr len -- actual )
+    virtiodev 0= IF nip EXIT THEN
     tuck
     0 ?DO
         dup c@ virtiodev SWAP virtio-serial-putchar
@@ -68,6 +70,7 @@ virtiodev virtio-serial-init drop
 
 : read ( addr len -- actual )
     0= IF drop 0 EXIT THEN
+    virtiodev 0= IF nip EXIT THEN
     virtiodev virtio-serial-haschar 0= IF 0 swap c! -2 EXIT THEN
     virtiodev virtio-serial-getchar swap c! 1
 ;