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

[Tim Gardner]

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

Free _manager on error lest memory become orphaned.

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

This patch applies to stable 3.5 and newer.

 drivers/gpu/drm/ttm/ttm_page_alloc.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c 
b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index bd2a3b4..2c73d0a 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");

@@ -817,6 +821,7 @@ int ttm_page_alloc_init(struct ttm_mem_global *glob, 
unsigned max_pages)
                                   &glob->kobj, "pool");
        if (unlikely(ret != 0)) {
                kobject_put(&_manager->kobj);
+               kfree(_manager);
                _manager = NULL;
                return ret;
        }
-- 
1.7.9.5