On Thu, Apr 01, 2021 at 12:00:39PM +0300, Dan Carpenter wrote:
> Hi Keith,
>
> I've been trying to figure out ways Smatch can check for device managed
> resources. Like adding rules that if we call dev_set_name(&foo->bar)
> then it's device managaged and if there is a kfree(foo) without calling
> device_put(&foo->bar) then that's a resource leak.
>
> Of course one of the rules is that if you call device_register(dev) then
> you can't kfree(dev), it has to released with device_put(dev) and that's
> true even if the register fails. But this code here feels very
> intentional so maybe there is an exception to the rule?
Thanks for the notice. There was no intentional use of this, so I
think it was a mistake. The proposal in the follow on replies looks much
better.
> The patch acc02a109b04: "node: Add memory-side caching attributes"
> from Mar 11, 2019, leads to the following static checker warning:
>
> drivers/base/node.c:285 node_init_cache_dev()
> error: kfree after device_register(): 'dev'
>
> drivers/base/node.c
> 263 static void node_init_cache_dev(struct node *node)
> 264 {
> 265 struct device *dev;
> 266
> 267 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> 268 if (!dev)
> 269 return;
> 270
> 271 dev->parent = &node->dev;
> 272 dev->release = node_cache_release;
> 273 if (dev_set_name(dev, "memory_side_cache"))
> 274 goto free_dev;
> 275
> 276 if (device_register(dev))
> ^^^^^^^^^^^^^^^^^^^
> 277 goto free_name;
> 278
> 279 pm_runtime_no_callbacks(dev);
> 280 node->cache_dev = dev;
> 281 return;
> 282 free_name:
> 283 kfree_const(dev->kobj.name);
> 284 free_dev:
> 285 kfree(dev);
> ^^^^^^^^^^
> 286 }
>
> regards,
> dan carpenter
