drm: use drms ioctl cmd not what we get passed from userspace.

This enforces us to use the drm ioctl types so read/write works correctly and not believe
what userspace tells us.

It does this hopefully without breaking the drm api.

Fixes bug from thread: BUG: unable to handle kernel NULL pointer dereference (drm_getunique)

Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/char/drm/drm_drv.c b/drivers/char/drm/drm_drv.c
index fc54140551a..22957ac15df 100644
--- a/drivers/char/drm/drm_drv.c
+++ b/drivers/char/drm/drm_drv.c
@@ -475,6 +475,8 @@ int drm_ioctl(struct inode *inode, struct file *filp,
         else
                 goto err_i1;
 
+        /* Do not trust userspace, use our own definition */
+        cmd = ioctl->cmd;
         func = ioctl->func;
         /* is there a local override? */
         if ((nr == DRM_IOCTL_NR(DRM_IOCTL_DMA)) && dev->driver->dma_ioctl)