linux-kernel - [patch 02/29] virtio: console: Dont access vqs if device was unplugged

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Date:	Thu, 10 Mar 2011 15:54:08 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Amit Shah <amit.shah@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: [patch 02/29] virtio: console: Dont access vqs if device was unplugged

2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Amit Shah <amit.shah@...hat.com>

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@...hat.com>
Signed-off-by: Amit Shah <amit.shah@...hat.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/char/virtio_console.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -387,6 +387,10 @@ static void discard_port_data(struct por
 	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(str
 	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;


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