openwrtv4/target/linux/brcm2708/patches-4.9/950-0181-drm-vc4-Fix-OOPSes-from-trying-to-cache-a-partially-.patch

From 3f131f18e76bb3fa56158adea3abddeaac68e860 Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Thu, 9 Feb 2017 09:23:34 -0800
Subject: [PATCH] drm/vc4: Fix OOPSes from trying to cache a partially
 constructed BO.

If a CMA allocation failed, the partially constructed BO would be
unreferenced through the normal path, and we might choose to put it in
the BO cache.  If we then reused it before it expired from the cache,
the kernel would OOPS.

Signed-off-by: Eric Anholt <eric@anholt.net>
Fixes: c826a6e10644 ("drm/vc4: Add a BO cache.")
---
 drivers/gpu/drm/vc4/vc4_bo.c | 8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/gpu/drm/vc4/vc4_bo.c
+++ b/drivers/gpu/drm/vc4/vc4_bo.c
@@ -322,6 +322,14 @@ void vc4_free_object(struct drm_gem_obje
 		goto out;
 	}
 
+	/* If this object was partially constructed but CMA allocation
+	 * had failed, just free it.
+	 */
+	if (!bo->base.vaddr) {
+		vc4_bo_destroy(bo);
+		goto out;
+	}
+
 	cache_list = vc4_get_cache_list_for_size(dev, gem_bo->size);
 	if (!cache_list) {
 		vc4_bo_destroy(bo);