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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 03711d00aaaea91d4225088f6311ad309dc262d1..8218078b61333134d1b3fb2de3d273e75245c5ef 100644 (file)
--- 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);