[PATCH 3.16 5/7] drm/vmwgfx: limit the number of mip levels in vmw_gb_surface_define_ioctl()

[Ben Hutchings <ben@decadent.org.uk>]

3.16.45-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vladis Dronov <vdronov@redhat.com>

commit ee9c4e681ec4f58e42a83cb0c22a0289ade1aacf upstream.

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@redhat.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -1251,6 +1251,9 @@ int vmw_gb_surface_define_ioctl(struct d
 	const struct svga3d_surface_desc *desc;
 	uint32_t backup_handle;
 
+	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;