drm: fix NULL pointer access by wrong ioctl

If user uses wrong ioctl command with _IOC_NONE and argument size
greater than 0, it can cause NULL pointer access from memset of line
463. If _IOC_NONE, don't memset to 0 for kdata.

Signed-off-by: Zhaowei Yuan <zhaowei.yuan@samsung.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 03711d00aaae..8218078b6133 100644..100755
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -419,8 +419,9 @@ long drm_ioctl(struct file *filp,
                         retcode = -EFAULT;
                         goto err_i1;
                 }
-        } else
+        } else if (cmd & IOC_OUT) {
                 memset(kdata, 0, usize);
+        }
 
         if (ioctl->flags & DRM_UNLOCKED)
                 retcode = func(dev, kdata, file_priv);