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

From: Jason Gunthorpe
Date: Fri Apr 16 2021 - 15:35:40 EST


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@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxx>

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