[PATCH 3.2 100/125] drm: fix NULL pointer access by wrong ioctl

Ben Hutchings
2014-07-08T19:44:23Z

From: Zhaowei Yuan <zhaowei.yuan@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@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>
---
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
@@ -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);