firewire: fix NULL pointer deref. and resource leak

By supplying ioctl()s in the wrong order, a userspace client was able to
trigger NULL pointer dereferences.  Furthermore, by calling
ioctl_create_iso_context more than once, new contexts could be created
without ever freeing the previously created contexts.

Thanks to Anders Blomdell for the report.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

diff --git a/drivers/firewire/fw-cdev.c b/drivers/firewire/fw-cdev.c
index 44ccee26c368b59c030b1b07a4b92c157fac4069..46bc197a047fe84329f4ec868e351ae0438cac2e 100644 (file)
--- a/drivers/firewire/fw-cdev.c
+++ b/drivers/firewire/fw-cdev.c
@@ -646,6 +646,10 @@ static int ioctl_create_iso_context(struct client *client, void *buffer)
        struct fw_cdev_create_iso_context *request = buffer;
        struct fw_iso_context *context;
 
+       /* We only support one context at this time. */
+       if (client->iso_context != NULL)
+               return -EBUSY;
+
        if (request->channel > 63)
                return -EINVAL;
 
@@ -792,8 +796,9 @@ static int ioctl_start_iso(struct client *client, void *buffer)
 {
        struct fw_cdev_start_iso *request = buffer;
 
-       if (request->handle != 0)
+       if (client->iso_context == NULL || request->handle != 0)
                return -EINVAL;
+
        if (client->iso_context->type == FW_ISO_CONTEXT_RECEIVE) {
                if (request->tags == 0 || request->tags > 15)
                        return -EINVAL;
@@ -810,7 +815,7 @@ static int ioctl_stop_iso(struct client *client, void *buffer)
 {
        struct fw_cdev_stop_iso *request = buffer;
 
-       if (request->handle != 0)
+       if (client->iso_context == NULL || request->handle != 0)
                return -EINVAL;
 
        return fw_iso_context_stop(client->iso_context);