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

commit d7a62cd0332115d4c7c4689abea0d889a30d8349 upstream.

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>
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index ad2520b1e03f418a1443db7581b04e0b936a989d..e0d94739ffd586599012267cad9d2497f27da904 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -387,6 +387,10 @@ 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;
@@ -469,6 +473,10 @@ 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;