[CVE-2017-7346][PATCH X/Y/Z/A] drm/vmwgfx: limit the number of mip levels in vmw_gb_surface_define_ioctl()

[Po-Hsu Lin]

From: Vladis Dronov <vdronov at redhat.com>

CVE-2017-7346

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

Cc: <stable at vger.kernel.org>
Signed-off-by: Vladis Dronov <vdronov at redhat.com>
Reviewed-by: Sinclair Yeh <syeh at vmware.com>
(cherry picked from commit ee9c4e681ec4f58e42a83cb0c22a0289ade1aacf)

Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
---
 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 05fa092..6fed5a8 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -1280,6 +1280,9 @@ 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;
-- 
1.7.9.5