[PATCH 3.11 030/128] drm: fix NULL pointer access by wrong ioctl

[Luis Henriques]

3.11.10.14 -stable review patch.  If anyone has any objections, please let me know.

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

From: Zhaowei Yuan <zhaowei.yuan at samsung.com>

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 at samsung.com>
Reviewed-by: David Herrmann <dh.herrmann at gmail.com>
Signed-off-by: Dave Airlie <airlied at redhat.com>
[ luis: backported to 3.11: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/gpu/drm/drm_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
 mode change 100644 => 100755 drivers/gpu/drm/drm_drv.c

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
old mode 100644
new mode 100755
index 6dd71735cab4..d71e1a46c4d4
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -460,8 +460,9 @@ 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);
-- 
1.9.1