drm/i915: Skip pread/pwrite if size to copy is 0.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index dba8202..29e97c0 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -576,7 +576,7 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
        struct drm_i915_gem_pread *args = data;
        struct drm_gem_object *obj;
        struct drm_i915_gem_object *obj_priv;
-       int ret;
+       int ret = 0;
 
        obj = drm_gem_object_lookup(dev, file_priv, args->handle);
        if (obj == NULL)
@@ -586,14 +586,17 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
        /* Bounds check source.  */
        if (args->offset > obj->size || args->size > obj->size - args->offset) {
                ret = -EINVAL;
-               goto err;
+               goto out;
        }
 
+       if (args->size == 0)
+               goto out;
+
        if (!access_ok(VERIFY_WRITE,
                       (char __user *)(uintptr_t)args->data_ptr,
                       args->size)) {
                ret = -EFAULT;
-               goto err;
+               goto out;
        }
 
        if (i915_gem_object_needs_bit17_swizzle(obj)) {
@@ -605,7 +608,7 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
                                                        file_priv);
        }
 
-err:
+out:
        drm_gem_object_unreference_unlocked(obj);
        return ret;
 }
@@ -1059,14 +1062,17 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
        /* Bounds check destination. */
        if (args->offset > obj->size || args->size > obj->size - args->offset) {
                ret = -EINVAL;
-               goto err;
+               goto out;
        }
 
+       if (args->size == 0)
+               goto out;
+
        if (!access_ok(VERIFY_READ,
                       (char __user *)(uintptr_t)args->data_ptr,
                       args->size)) {
                ret = -EFAULT;
-               goto err;
+               goto out;
        }
 
        /* We can only do the GTT pwrite on untiled buffers, as otherwise
@@ -1100,7 +1106,7 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
                DRM_INFO("pwrite failed %d\n", ret);
 #endif
 
-err:
+out:
        drm_gem_object_unreference_unlocked(obj);
        return ret;
 }