drm: Break out ioctl permission check to a separate function v2

Helps reviewing and understanding these checks.
v2: Remove misplaced newlines.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
(cherry picked from commit c2667355619572c9324916b62b4f6608a56de031)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 345be03..002596c 100644 (file)
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -286,6 +286,44 @@ static int drm_version(struct drm_device *dev, void *data,
 }
 
 /**
+ * drm_ioctl_permit - Check ioctl permissions against caller
+ *
+ * @flags: ioctl permission flags.
+ * @file_priv: Pointer to struct drm_file identifying the caller.
+ *
+ * Checks whether the caller is allowed to run an ioctl with the
+ * indicated permissions. If so, returns zero. Otherwise returns an
+ * error code suitable for ioctl return.
+ */
+static int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
+{
+       /* ROOT_ONLY is only for CAP_SYS_ADMIN */
+       if (unlikely((flags & DRM_ROOT_ONLY) && !capable(CAP_SYS_ADMIN)))
+               return -EACCES;
+
+       /* AUTH is only for authenticated or render client */
+       if (unlikely((flags & DRM_AUTH) && !drm_is_render_client(file_priv) &&
+                    !file_priv->authenticated))
+               return -EACCES;
+
+       /* MASTER is only for master */
+       if (unlikely((flags & DRM_MASTER) && !file_priv->is_master))
+               return -EACCES;
+
+       /* Control clients must be explicitly allowed */
+       if (unlikely(!(flags & DRM_CONTROL_ALLOW) &&
+                    file_priv->minor->type == DRM_MINOR_CONTROL))
+               return -EACCES;
+
+       /* Render clients must be explicitly allowed */
+       if (unlikely(!(flags & DRM_RENDER_ALLOW) &&
+                    drm_is_render_client(file_priv)))
+               return -EACCES;
+
+       return 0;
+}
+
+/**
  * Called whenever a process performs an ioctl on /dev/drm.
  *
  * \param inode device inode.
@@ -350,52 +388,51 @@ long drm_ioctl(struct file *filp,
        /* Do not trust userspace, use our own definition */
        func = ioctl->func;
 
-       if (!func) {
+       if (unlikely(!func)) {
                DRM_DEBUG("no function\n");
                retcode = -EINVAL;
-       } else if (((ioctl->flags & DRM_ROOT_ONLY) && !capable(CAP_SYS_ADMIN)) ||
-                  ((ioctl->flags & DRM_AUTH) && !drm_is_render_client(file_priv) && !file_priv->authenticated) ||
-                  ((ioctl->flags & DRM_MASTER) && !file_priv->is_master) ||
-                  (!(ioctl->flags & DRM_CONTROL_ALLOW) && (file_priv->minor->type == DRM_MINOR_CONTROL)) ||
-                  (!(ioctl->flags & DRM_RENDER_ALLOW) && drm_is_render_client(file_priv))) {
-               retcode = -EACCES;
-       } else {
-               if (cmd & (IOC_IN | IOC_OUT)) {
-                       if (asize <= sizeof(stack_kdata)) {
-                               kdata = stack_kdata;
-                       } else {
-                               kdata = kmalloc(asize, GFP_KERNEL);
-                               if (!kdata) {
-                                       retcode = -ENOMEM;
-                                       goto err_i1;
-                               }
-                       }
-                       if (asize > usize)
-                               memset(kdata + usize, 0, asize - usize);
-               }
+               goto err_i1;
+       }
 
-               if (cmd & IOC_IN) {
-                       if (copy_from_user(kdata, (void __user *)arg,
-                                          usize) != 0) {
-                               retcode = -EFAULT;
+       retcode = drm_ioctl_permit(ioctl->flags, file_priv);
+       if (unlikely(retcode))
+               goto err_i1;
+
+       if (cmd & (IOC_IN | IOC_OUT)) {
+               if (asize <= sizeof(stack_kdata)) {
+                       kdata = stack_kdata;
+               } else {
+                       kdata = kmalloc(asize, GFP_KERNEL);
+                       if (!kdata) {
+                               retcode = -ENOMEM;
                                goto err_i1;
                        }
-               } else
-                       memset(kdata, 0, usize);
-
-               if (ioctl->flags & DRM_UNLOCKED)
-                       retcode = func(dev, kdata, file_priv);
-               else {
-                       mutex_lock(&drm_global_mutex);
-                       retcode = func(dev, kdata, file_priv);
-                       mutex_unlock(&drm_global_mutex);
                }
+               if (asize > usize)
+                       memset(kdata + usize, 0, asize - usize);
+       }
 
-               if (cmd & IOC_OUT) {
-                       if (copy_to_user((void __user *)arg, kdata,
-                                        usize) != 0)
-                               retcode = -EFAULT;
+       if (cmd & IOC_IN) {
+               if (copy_from_user(kdata, (void __user *)arg,
+                                  usize) != 0) {
+                       retcode = -EFAULT;
+                       goto err_i1;
                }
+       } else
+               memset(kdata, 0, usize);
+
+       if (ioctl->flags & DRM_UNLOCKED)
+               retcode = func(dev, kdata, file_priv);
+       else {
+               mutex_lock(&drm_global_mutex);
+               retcode = func(dev, kdata, file_priv);
+               mutex_unlock(&drm_global_mutex);
+       }
+
+       if (cmd & IOC_OUT) {
+               if (copy_to_user((void __user *)arg, kdata,
+                                usize) != 0)
+                       retcode = -EFAULT;
        }
 
       err_i1: