[media] cx88: hold device lock during sub-driver initialization

cx8802_blackbird_probe makes a device node for the mpeg sub-device
before it has been added to dev->drvlist.  If the device is opened
during that time, the open succeeds but request_acquire cannot be
called, so the reference count remains zero.  Later, when the device
is closed, the reference count becomes negative --- uh oh.

Close the race by holding core->lock during probe and not releasing
until the device is in drvlist and initialization finished.
Previously the BKL prevented this race.

Reported-by: Andreas Huber <hobrom@gmx.at>
Tested-by: Andi Huber <hobrom@gmx.at>
Tested-by: Marlon de Boer <marlon@hyves.nl>
Cc: stable@kernel.org
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

3 files changed, 4 insertions, 10 deletions

diff --git a/drivers/media/video/cx88/cx88-blackbird.c b/drivers/media/video/cx88/cx88-blackbird.c
index a6f7d53a4510..f637d34d5062 100644
--- a/drivers/media/video/cx88/cx88-blackbird.c
+++ b/drivers/media/video/cx88/cx88-blackbird.c
@@ -1335,11 +1335,9 @@ static int cx8802_blackbird_probe(struct cx8802_driver *drv)
         blackbird_register_video(dev);
 
         /* initial device configuration: needed ? */
-        mutex_lock(&dev->core->lock);
 //      init_controls(core);
         cx88_set_tvnorm(core,core->tvnorm);
         cx88_video_mux(core,0);
-        mutex_unlock(&dev->core->lock);
 
         return 0;
 
diff --git a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c
index 91d3d179c3c7..455290011d4e 100644
--- a/drivers/media/video/cx88/cx88-mpeg.c
+++ b/drivers/media/video/cx88/cx88-mpeg.c
@@ -709,18 +709,17 @@ int cx8802_register_driver(struct cx8802_driver *drv)
                 drv->request_release = cx8802_request_release;
                 memcpy(driver, drv, sizeof(*driver));
 
+                mutex_lock(&drv->core->lock);
                 err = drv->probe(driver);
                 if (err == 0) {
                         i++;
-                        mutex_lock(&drv->core->lock);
                         list_add_tail(&driver->drvlist, &dev->drvlist);
-                        mutex_unlock(&drv->core->lock);
                 } else {
                         printk(KERN_ERR
                                "%s/2: cx8802 probe failed, err = %d\n",
                                dev->core->name, err);
                 }
-
+                mutex_unlock(&drv->core->lock);
         }
 
         return i ? 0 : -ENODEV;
diff --git a/drivers/media/video/cx88/cx88.h b/drivers/media/video/cx88/cx88.h
index 9731daa92a06..3d32f4afac9d 100644
--- a/drivers/media/video/cx88/cx88.h
+++ b/drivers/media/video/cx88/cx88.h
@@ -505,13 +505,10 @@ struct cx8802_driver {
         int (*suspend)(struct pci_dev *pci_dev, pm_message_t state);
         int (*resume)(struct pci_dev *pci_dev);
 
-        /* MPEG 8802 -> mini driver - Driver probe and configuration */
-
-        /* Caller must _not_ hold core->lock */
-        int (*probe)(struct cx8802_driver *drv);
-
         /* Callers to the following functions must hold core->lock */
 
+        /* MPEG 8802 -> mini driver - Driver probe and configuration */
+        int (*probe)(struct cx8802_driver *drv);
         int (*remove)(struct cx8802_driver *drv);
 
         /* MPEG 8802 -> mini driver - Access for hardware control */