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

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

From: Zhaowei Yuan <[email protected]>

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 <[email protected]>
Reviewed-by: David Herrmann <[email protected]>
Signed-off-by: Dave Airlie <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 drivers/gpu/drm/drm_drv.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 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);


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