From: Amit Shah <amit.shah@redhat.com>
Date: Fri, 4 Mar 2011 03:34:33 +0000 (+1030)
Subject: virtio: console: Don't access vqs if device was unplugged
X-Git-Tag: v2.6.37.4~29
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=310f5e480c6facfdf9ee9e6952e490eebd3d8d55;p=thirdparty%2Fkernel%2Fstable.git

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 ad2520b1e03f4..e0d94739ffd58 100644
--- 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;