[PATCH] drm/vmwgfx: Fix possible usage of an uninitialized variable

[Zack Rusin]

From: Zack Rusin <zackr at vmware.com>

vmw_user_bo_lookup can fail to lookup user buffers, especially because
the buffer handles come from the userspace. The return value has
to be checked before the buffers are put back.

This was spotted by Dan's Smatch statick checker:
    drivers/gpu/drm/vmwgfx/vmwgfx_bo.c:574 vmw_user_bo_synccpu_release()
	error: uninitialized symbol 'vmw_bo'.

Signed-off-by: Zack Rusin <zackr at vmware.com>
Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
Fixes: 8afa13a0583f ("drm/vmwgfx: Implement DRIVER_GEM")
---
 drivers/gpu/drm/vmwgfx/vmwgfx_bo.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c b/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
index 15fead85450c..31aecc46624b 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
@@ -568,10 +568,12 @@ static int vmw_user_bo_synccpu_release(struct drm_file *filp,
 	struct vmw_buffer_object *vmw_bo;
 	int ret = vmw_user_bo_lookup(filp, handle, &vmw_bo);
 
-	if (!(flags & drm_vmw_synccpu_allow_cs)) {
-		atomic_dec(&vmw_bo->cpu_writers);
+	if (!ret) {
+		if (!(flags & drm_vmw_synccpu_allow_cs)) {
+			atomic_dec(&vmw_bo->cpu_writers);
+		}
+		ttm_bo_put(&vmw_bo->base);
 	}
-	ttm_bo_put(&vmw_bo->base);
 
 	return ret;
 }
-- 
2.32.0