[PATCH v2] kernel: drm/vmwgfx: limit the number of mip levels in vmw_gb_surface_define_ioctl()

[Vladis Dronov]

The 'req->mip_levels' parameter in vmw_gb_surface_define_ioctl() is
a user-controlled 'uint32_t' value which is used as a loop count limit.
This can lead to a kernel lockup and DoS. Add check for 'req->mip_levels'.

References:
https://bugzilla.redhat.com/show_bug.cgi?id=1437431
Signed-off-by: Vladis Dronov <vdronov@xxxxxxxxxx>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index b445ce9..e0d7ff9 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -1281,6 +1281,9 @@ int vmw_gb_surface_define_ioctl(struct drm_device *dev, void *data,
 	if (req->multisample_count != 0)
 		return -EINVAL;
 
+	if (req->mip_levels > DRM_VMW_MAX_MIP_LEVELS)
+		return -EINVAL;
+
 	if (unlikely(vmw_user_surface_size == 0))
 		vmw_user_surface_size = ttm_round_pot(sizeof(*user_srf)) +
 			128;
-- 
2.9.3