From: Julia Lawall Date: Sat, 15 May 2010 09:45:53 +0000 (+0200) Subject: drivers/char: Eliminate use after free X-Git-Tag: v2.6.35-rc1~435^2 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=0643e4c6e4fd67778fa886a89e6ec2320e0ff4d3 drivers/char: Eliminate use after free In each case, the first argument to send_control_msg or __send_control_msg, respectively, has either not been successfully allocated or has been freed at the point of the call. In the first case, the first argument, port, is only used to access the portdev and id fields, in order to call __send_control_msg. Thus it seems possible instead to call __send_control_msg directly. In the second case, the call to __send_control_msg is moved up to a place where it seems like the first argument, portdev, has been initialized sufficiently to make the call to __send_control_msg meaningful. This has only been compile tested. A simplified version of the semantic match that finds this problem is as follows: (http://coccinelle.lip6.fr/) // @free@ expression E; position p; @@ kfree@p(E) @@ expression free.E, subE<=free.E, E1; position free.p; @@ kfree@p(E) ... ( subE = E1 | * E ) // Signed-off-by: Julia Lawall Acked-by: Amit Shah Signed-off-by: Rusty Russell --- diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 458d907e3621..8c99bf1b5e9f 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1090,7 +1090,7 @@ free_port: kfree(port); fail: /* The host might want to notify management sw about port add failure */ - send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 0); + __send_control_msg(portdev, id, VIRTIO_CONSOLE_PORT_READY, 0); return err; } @@ -1559,6 +1559,9 @@ static int __devinit virtcons_probe(struct virtio_device *vdev) return 0; free_vqs: + /* The host might want to notify mgmt sw about device add failure */ + __send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID, + VIRTIO_CONSOLE_DEVICE_READY, 0); vdev->config->del_vqs(vdev); kfree(portdev->in_vqs); kfree(portdev->out_vqs); @@ -1567,9 +1570,6 @@ free_chrdev: free: kfree(portdev); fail: - /* The host might want to notify mgmt sw about device add failure */ - __send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID, - VIRTIO_CONSOLE_DEVICE_READY, 0); return err; }