drm: fix NULL pointer access by wrong ioctl

commit 1539fb9bd405ee32282ea0a38404f9e008ac5b7a upstream.

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>
Signed-off-by: Dave Airlie <airlied@redhat.com>
[bwh: Backported to 3.2: adjust indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index acfe567..0731d43 100644 (file)
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -456,8 +456,9 @@ 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);