virtio: console: Don't access vqs if device was unplugged

If a virtio-console device gets unplugged while a port is open, a
subsequent close() call on the port accesses vqs to free up buffers.
This can lead to a crash.

The buffers are already freed up as a result of the call to
unplug_ports() from virtcons_remove().  The fix is to simply not access
vq information if port->portdev is NULL.

Reported-by: juzhang <juzhang@redhat.com>
CC: stable@kernel.org
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 490393186338dae5b8a7a7804923b801a381263a..84b164d1eb2b16d29db4d87ed6a7d745fa1938bc 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -388,6 +388,10 @@ static void discard_port_data(struct port *port)
        unsigned int len;
        int ret;
 
+       if (!port->portdev) {
+               /* Device has been unplugged.  vqs are already gone. */
+               return;
+       }
        vq = port->in_vq;
        if (port->inbuf)
                buf = port->inbuf;
@@ -470,6 +474,10 @@ static void reclaim_consumed_buffers(struct port *port)
        void *buf;
        unsigned int len;
 
+       if (!port->portdev) {
+               /* Device has been unplugged.  vqs are already gone. */
+               return;
+       }
        while ((buf = virtqueue_get_buf(port->out_vq, &len))) {
                kfree(buf);
                port->outvq_full = false;