[media] uvcvideo: Remove sysadmin requirements for UVCIOC_CTRL_MAP

This patch removes the sysadmin requirements for UVCIOC_CTRL_MAP (and the stub
implementation of UVCIOC_CTRL_ADD). This requirement no longer makes sense with
the new XU control access mechanisms since XU controls can be accessed without
adding control mappings first.

A maximum number (currently 1024) of control mappings per device is enforced to
avoid excess memory consumption caused by careless user space applications.

Signed-off-by: Martin Rubli <martin_rubli@logitech.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

4 files changed, 19 insertions, 6 deletions

diff --git a/drivers/media/video/uvc/uvc_ctrl.c b/drivers/media/video/uvc/uvc_ctrl.c
index 2c81b7f3555..531a3e1a6d1 100644
--- a/drivers/media/video/uvc/uvc_ctrl.c
+++ b/drivers/media/video/uvc/uvc_ctrl.c
@@ -1435,6 +1435,7 @@ int uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
         struct uvc_entity *entity;
         struct uvc_control *ctrl;
         int found = 0;
+        int ret;
 
         if (mapping->id & ~V4L2_CTRL_ID_MASK) {
                 uvc_trace(UVC_TRACE_CONTROL, "Can't add mapping '%s', control "
@@ -1478,7 +1479,20 @@ int uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
                 }
         }
 
+        /* Prevent excess memory consumption */
+        if (atomic_inc_return(&dev->nmappings) > UVC_MAX_CONTROL_MAPPINGS) {
+                atomic_dec(&dev->nmappings);
+                uvc_trace(UVC_TRACE_CONTROL, "Can't add mapping '%s', maximum "
+                        "mappings count (%u) exceeded.\n", mapping->name,
+                        UVC_MAX_CONTROL_MAPPINGS);
+                ret = -ENOMEM;
+                goto done;
+        }
+
         ret = __uvc_ctrl_add_mapping(dev, ctrl, mapping);
+        if (ret < 0)
+                atomic_dec(&dev->nmappings);
+
 done:
         mutex_unlock(&chain->ctrl_mutex);
         return ret;
diff --git a/drivers/media/video/uvc/uvc_driver.c b/drivers/media/video/uvc/uvc_driver.c
index 71efda76cc7..a1e9dfb52f6 100644
--- a/drivers/media/video/uvc/uvc_driver.c
+++ b/drivers/media/video/uvc/uvc_driver.c
@@ -1760,6 +1760,7 @@ static int uvc_probe(struct usb_interface *intf,
         INIT_LIST_HEAD(&dev->streams);
         atomic_set(&dev->nstreams, 0);
         atomic_set(&dev->users, 0);
+        atomic_set(&dev->nmappings, 0);
 
         dev->udev = usb_get_dev(udev);
         dev->intf = usb_get_intf(intf);
diff --git a/drivers/media/video/uvc/uvc_v4l2.c b/drivers/media/video/uvc/uvc_v4l2.c
index 4a510483f7c..6d15de9b520 100644
--- a/drivers/media/video/uvc/uvc_v4l2.c
+++ b/drivers/media/video/uvc/uvc_v4l2.c
@@ -1025,16 +1025,10 @@ static long uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
         /* Dynamic controls. */
         case UVCIOC_CTRL_ADD:
                 /* Legacy ioctl, kept for API compatibility reasons */
-                if (!capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-
                 return -EEXIST;
 
         case UVCIOC_CTRL_MAP_OLD:
         case UVCIOC_CTRL_MAP:
-                if (!capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-
                 return uvc_ioctl_ctrl_map(chain, arg,
                                           cmd == UVCIOC_CTRL_MAP_OLD);
 
diff --git a/drivers/media/video/uvc/uvcvideo.h b/drivers/media/video/uvc/uvcvideo.h
index 34637fbbbd6..39e9e36e883 100644
--- a/drivers/media/video/uvc/uvcvideo.h
+++ b/drivers/media/video/uvc/uvcvideo.h
@@ -172,6 +172,9 @@ struct uvc_xu_control {
 #define UVC_CTRL_CONTROL_TIMEOUT        300
 #define UVC_CTRL_STREAMING_TIMEOUT      5000
 
+/* Maximum allowed number of control mappings per device */
+#define UVC_MAX_CONTROL_MAPPINGS        1024
+
 /* Devices quirks */
 #define UVC_QUIRK_STATUS_INTERVAL       0x00000001
 #define UVC_QUIRK_PROBE_MINMAX          0x00000002
@@ -472,6 +475,7 @@ struct uvc_device {
 
         enum uvc_device_state state;
         atomic_t users;
+        atomic_t nmappings;
 
         /* Video control interface */
         __u16 uvc_version;