drm/i915/userptr: reject zero user_size

Operating on a zero sized GEM userptr object will lead to explosions.

Fixes: 5cc9ed4b9a7a ("drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl")
Testcase: igt/gem_userptr_blits/input-checking
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180502195021.30900-1-matthew.auld@intel.com
(cherry picked from commit c11c7bfd213495784b22ef82a69b6489f8d0092f)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index d596a8302ca3..854bd51b9478 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -778,6 +778,9 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
                             I915_USERPTR_UNSYNCHRONIZED))
                 return -EINVAL;
 
+        if (!args->user_size)
+                return -EINVAL;
+
         if (offset_in_page(args->user_ptr | args->user_size))
                 return -EINVAL;