[ 03/12] virtio: console: fix race in port_fops_open() and port unplug

Greg Kroah-Hartman
2013-08-13T06:42:19Z

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

commit 671bdea2b9f210566610603ecbb6584c8a201c8c upstream.

Between open() being called and processed, the port can be unplugged.
Check if this happened, and bail out.

A simple test script to reproduce this is:

while true; do for i in $(seq 1 100); do echo $i > /dev/vport0p3; done; done;

This opens and closes the port a lot of times; unplugging the port while
this is happening triggers the bug.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/char/virtio_console.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -786,6 +786,10 @@ static int port_fops_open(struct inode *

/* We get the port with a kref here */
port = find_port_by_devt(cdev->dev);
+ if (!port) {
+ /* Port was unplugged before we could proceed */
+ return -ENXIO;
+ }
filp->private_data = port;

/*