V4L/DVB (9668): em28xx: fix a race condition with hald

Newer versions of hald tries to open it to call QUERYCAP.

Due to the lack of a proper locking, it is possible to open the device
before it finishes initialization.

This patch adds a lock to avoid this risk, and to protect the list of
em28xx devices.

While here, remove the uneeded BKL lock.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 75 insertions, 53 deletions

diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index c32fc7d24a42..90a11b5ac0b1 100644
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -73,6 +73,7 @@ MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_LICENSE("GPL");
 
 static LIST_HEAD(em28xx_devlist);
+static DEFINE_MUTEX(em28xx_devlist_mutex);
 
 static unsigned int card[]     = {[0 ... (EM28XX_MAXBOARDS - 1)] = UNSET };
 static unsigned int video_nr[] = {[0 ... (EM28XX_MAXBOARDS - 1)] = UNSET };
@@ -1519,7 +1520,7 @@ static int em28xx_v4l2_open(struct inode *inode, struct file *filp)
         struct em28xx_fh *fh;
         enum v4l2_buf_type fh_type = 0;
 
-        lock_kernel();
+        mutex_lock(&em28xx_devlist_mutex);
         list_for_each_entry(h, &em28xx_devlist, devlist) {
                 if (h->vdev->minor == minor) {
                         dev  = h;
@@ -1535,10 +1536,11 @@ static int em28xx_v4l2_open(struct inode *inode, struct file *filp)
                         dev   = h;
                 }
         }
-        if (NULL == dev) {
-                unlock_kernel();
+        mutex_unlock(&em28xx_devlist_mutex);
+        if (NULL == dev)
                 return -ENODEV;
-        }
+
+        mutex_lock(&dev->lock);
 
         em28xx_videodbg("open minor=%d type=%s users=%d\n",
                                 minor, v4l2_type_names[fh_type], dev->users);
@@ -1547,10 +1549,9 @@ static int em28xx_v4l2_open(struct inode *inode, struct file *filp)
         fh = kzalloc(sizeof(struct em28xx_fh), GFP_KERNEL);
         if (!fh) {
                 em28xx_errdev("em28xx-video.c: Out of memory?!\n");
-                unlock_kernel();
+                mutex_unlock(&dev->lock);
                 return -ENOMEM;
         }
-        mutex_lock(&dev->lock);
         fh->dev = dev;
         fh->radio = radio;
         fh->type = fh_type;
@@ -1584,7 +1585,6 @@ static int em28xx_v4l2_open(struct inode *inode, struct file *filp)
                         sizeof(struct em28xx_buffer), fh);
 
         mutex_unlock(&dev->lock);
-        unlock_kernel();
 
         return errCode;
 }
@@ -1871,6 +1871,7 @@ int em28xx_register_extension(struct em28xx_ops *ops)
 {
         struct em28xx *dev = NULL;
 
+        mutex_lock(&em28xx_devlist_mutex);
         mutex_lock(&em28xx_extension_devlist_lock);
         list_add_tail(&ops->next, &em28xx_extension_devlist);
         list_for_each_entry(dev, &em28xx_devlist, devlist) {
@@ -1879,6 +1880,7 @@ int em28xx_register_extension(struct em28xx_ops *ops)
         }
         printk(KERN_INFO "Em28xx: Initialized (%s) extension\n", ops->name);
         mutex_unlock(&em28xx_extension_devlist_lock);
+        mutex_unlock(&em28xx_devlist_mutex);
         return 0;
 }
 EXPORT_SYMBOL(em28xx_register_extension);
@@ -1887,6 +1889,7 @@ void em28xx_unregister_extension(struct em28xx_ops *ops)
 {
         struct em28xx *dev = NULL;
 
+        mutex_lock(&em28xx_devlist_mutex);
         list_for_each_entry(dev, &em28xx_devlist, devlist) {
                 if (dev)
                         ops->fini(dev);
@@ -1896,6 +1899,7 @@ void em28xx_unregister_extension(struct em28xx_ops *ops)
         printk(KERN_INFO "Em28xx: Removed (%s) extension\n", ops->name);
         list_del(&ops->next);
         mutex_unlock(&em28xx_extension_devlist_lock);
+        mutex_unlock(&em28xx_devlist_mutex);
 }
 EXPORT_SYMBOL(em28xx_unregister_extension);
 
@@ -1921,6 +1925,60 @@ static struct video_device *em28xx_vdev_init(struct em28xx *dev,
 }
 
 
+static int register_analog_devices(struct em28xx *dev)
+{
+        int ret;
+
+        /* allocate and fill video video_device struct */
+        dev->vdev = em28xx_vdev_init(dev, &em28xx_video_template, "video");
+        if (!dev->vdev) {
+                em28xx_errdev("cannot allocate video_device.\n");
+                return -ENODEV;
+        }
+
+        /* register v4l2 video video_device */
+        ret = video_register_device(dev->vdev, VFL_TYPE_GRABBER,
+                                       video_nr[dev->devno]);
+        if (ret) {
+                em28xx_errdev("unable to register video device (error=%i).\n",
+                              ret);
+                return ret;
+        }
+
+        /* Allocate and fill vbi video_device struct */
+        dev->vbi_dev = em28xx_vdev_init(dev, &em28xx_video_template, "vbi");
+
+        /* register v4l2 vbi video_device */
+        ret = video_register_device(dev->vbi_dev, VFL_TYPE_VBI,
+                                        vbi_nr[dev->devno]);
+        if (ret < 0) {
+                em28xx_errdev("unable to register vbi device\n");
+                return ret;
+        }
+
+        if (em28xx_boards[dev->model].radio.type == EM28XX_RADIO) {
+                dev->radio_dev = em28xx_vdev_init(dev, &em28xx_radio_template, "radio");
+                if (!dev->radio_dev) {
+                        em28xx_errdev("cannot allocate video_device.\n");
+                        return -ENODEV;
+                }
+                ret = video_register_device(dev->radio_dev, VFL_TYPE_RADIO,
+                                            radio_nr[dev->devno]);
+                if (ret < 0) {
+                        em28xx_errdev("can't register radio device\n");
+                        return ret;
+                }
+                em28xx_info("Registered radio device as /dev/radio%d\n",
+                            dev->radio_dev->num);
+        }
+
+        em28xx_info("V4L2 device registered as /dev/video%d and /dev/vbi%d\n",
+                                dev->vdev->num, dev->vbi_dev->num);
+
+        return 0;
+}
+
+
 /*
  * em28xx_init_dev()
  * allocates and inits the device structs, registers i2c bus and v4l device
@@ -2000,50 +2058,6 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
                 return errCode;
         }
 
-        list_add_tail(&dev->devlist, &em28xx_devlist);
-
-        /* allocate and fill video video_device struct */
-        dev->vdev = em28xx_vdev_init(dev, &em28xx_video_template, "video");
-        if (NULL == dev->vdev) {
-                em28xx_errdev("cannot allocate video_device.\n");
-                goto fail_unreg;
-        }
-
-        /* register v4l2 video video_device */
-        retval = video_register_device(dev->vdev, VFL_TYPE_GRABBER,
-                                       video_nr[dev->devno]);
-        if (retval) {
-                em28xx_errdev("unable to register video device (error=%i).\n",
-                              retval);
-                goto fail_unreg;
-        }
-
-        /* Allocate and fill vbi video_device struct */
-        dev->vbi_dev = em28xx_vdev_init(dev, &em28xx_video_template, "vbi");
-        /* register v4l2 vbi video_device */
-        if (video_register_device(dev->vbi_dev, VFL_TYPE_VBI,
-                                        vbi_nr[dev->devno]) < 0) {
-                em28xx_errdev("unable to register vbi device\n");
-                retval = -ENODEV;
-                goto fail_unreg;
-        }
-
-        if (em28xx_boards[dev->model].radio.type == EM28XX_RADIO) {
-                dev->radio_dev = em28xx_vdev_init(dev, &em28xx_radio_template, "radio");
-                if (NULL == dev->radio_dev) {
-                        em28xx_errdev("cannot allocate video_device.\n");
-                        goto fail_unreg;
-                }
-                retval = video_register_device(dev->radio_dev, VFL_TYPE_RADIO,
-                                            radio_nr[dev->devno]);
-                if (retval < 0) {
-                        em28xx_errdev("can't register radio device\n");
-                        goto fail_unreg;
-                }
-                em28xx_info("Registered radio device as /dev/radio%d\n",
-                            dev->radio_dev->num);
-        }
-
         /* init video dma queues */
         INIT_LIST_HEAD(&dev->vidq.active);
         INIT_LIST_HEAD(&dev->vidq.queued);
@@ -2070,8 +2084,14 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
 
         video_mux(dev, 0);
 
-        em28xx_info("V4L2 device registered as /dev/video%d and /dev/vbi%d\n",
-                                dev->vdev->num, dev->vbi_dev->num);
+        mutex_lock(&em28xx_devlist_mutex);
+        list_add_tail(&dev->devlist, &em28xx_devlist);
+        retval = register_analog_devices(dev);
+        if (retval < 0) {
+                em28xx_release_resources(dev);
+                mutex_unlock(&em28xx_devlist_mutex);
+                goto fail_reg_devices;
+        }
 
         mutex_lock(&em28xx_extension_devlist_lock);
         if (!list_empty(&em28xx_extension_devlist)) {
@@ -2081,11 +2101,13 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
                 }
         }
         mutex_unlock(&em28xx_extension_devlist_lock);
+        mutex_unlock(&em28xx_devlist_mutex);
 
         return 0;
 
 fail_unreg:
         em28xx_release_resources(dev);
+fail_reg_devices:
         mutex_unlock(&dev->lock);
         return retval;
 }