[PATCH v2 3.7-rc8] ttm: Fix possible _manager memory allocation oops

[Tim Gardner <tim.gardner@canonical.com>]

Memory for _manager is allocated using kzalloc() but the result is not checked.

I was led to scrutinize ttm_page_alloc_init() from a smatch warning:

drivers/gpu/drm/ttm/ttm_page_alloc.c:799 ttm_page_alloc_init() error: potential null dereference '_manager'.  (kzalloc returns null)

Cc: David Airlie <airlied@linux.ie>
Cc: Dave Airlie <airlied@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Zhao Yakui <yakui.zhao@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: stable@vger.kernel.org # 3.5+
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---

This patch applies to stable 3.5 and newer.

V2 - kobject_put(&_manager->kobj) uses a destructor and
container_of() to free _mamanger.

 drivers/gpu/drm/ttm/ttm_page_alloc.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index bd2a3b4..c64e96c 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
@@ -798,6 +798,10 @@ int ttm_page_alloc_init(struct ttm_mem_global *glob, unsigned max_pages)
 	pr_info("Initializing pool allocator\n");
 
 	_manager = kzalloc(sizeof(*_manager), GFP_KERNEL);
+	if (!_manager) {
+		pr_err("ttm: Could not allocate _manager.\n");
+		return -ENOMEM;
+	}
 
 	ttm_page_pool_init_locked(&_manager->wc_pool, GFP_HIGHUSER, "wc");
 
-- 
1.7.9.5