linux-kernel - [bug report] node: Add memory-side caching attributes

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Message-ID: <YGWLtzMLqSW4cxma@mwanda>
Date:   Thu, 1 Apr 2021 12:00:39 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbusch@...nel.org
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Jason Gunthorpe <jgg@...dia.com>
Subject: [bug report] node: Add memory-side caching attributes

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?

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