linux-kernel - Re: [PATCH] node: fix device cleanups in error handling code

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Date:   Fri, 16 Apr 2021 16:35:35 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Brice Goglin <Brice.Goglin@...ia.fr>,
        Keith Busch <kbusch@...nel.org>, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] node: fix device cleanups in error handling code

On Fri, Apr 09, 2021 at 02:01:57PM +0300, Dan Carpenter wrote:
> We can't use kfree() to free device managed resources so the kfree(dev)
> is against the rules.
> 
> It's easier to write this code if we open code the device_register() as
> a device_initialize() and device_add().  That way if dev_set_name() set
> name fails we can call put_device() and it will clean up correctly.
> 
> Fixes: acc02a109b04 ("node: Add memory-side caching attributes")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
>  drivers/base/node.c | 26 ++++++++++++--------------
>  1 file changed, 12 insertions(+), 14 deletions(-)

Wow, yikes, that "kfree_const(dev->kobj.name);" is really creative

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Though I dislike ignoring the error code from dev_set_name(), I think
Greg would prefer this:

diff --git a/drivers/base/node.c b/drivers/base/node.c
index f449dbb2c74666..80079e440add12 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -140,20 +140,16 @@ static struct node_access_nodes *node_init_node_access(struct node *node,
 	dev->parent = &node->dev;
 	dev->release = node_access_release;
 	dev->groups = node_access_node_groups;
-	if (dev_set_name(dev, "access%u", access))
-		goto free;
 
-	if (device_register(dev))
-		goto free_name;
+	dev_set_name(dev, "access%u", access);
+	if (device_register(dev)) {
+		put_device(dev);
+		return NULL;
+	}
 
 	pm_runtime_no_callbacks(dev);
 	list_add_tail(&access_node->list_node, &node->access_list);
 	return access_node;
-free_name:
-	kfree_const(dev->kobj.name);
-free:
-	kfree(access_node);
-	return NULL;
 }
 

(arguably a device_register_name() would be even better, if you are
handy with coccinelle there could quickly be alot of users)

Jason