linux-kernel - Re: [PATCH] drivers/base/node: Fix double free in register_one

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Message-ID: <5512b1b6-31f8-4322-8a5f-add8d1e9b22f@redhat.com>
Date: Thu, 18 Sep 2025 07:55:07 +0200
From: David Hildenbrand <david@...hat.com>
To: Donet Tom <donettom@...ux.ibm.com>, akpm@...ux-foundation.org,
 clm@...a.com
Cc: Jonathan.Cameron@...wei.com, alison.schofield@...el.com, dakr@...nel.org,
 dave.jiang@...el.com, gregkh@...uxfoundation.org,
 kamezawa.hiroyu@...fujitsu.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, osalvador@...e.de, rafael@...nel.org,
 ritesh.list@...il.com, yury.norov@...il.com, ziy@...dia.com
Subject: Re: [PATCH] drivers/base/node: Fix double free in register_one_node()

On 18.09.25 07:41, Donet Tom wrote:
> When device_register() fails in register_node(), it calls
> put_device(&node->dev). This triggers node_device_release(),
> which calls kfree(to_node(dev)), thereby freeing the entire
> node structure.
> 
> As a result, when register_node() returns an error, the node
> memory has already been freed. Calling kfree(node) again in
> register_one_node() leads to a double free.
> 
> This patch removes the redundant kfree(node) from
> register_one_node() to prevent the double free.
> 
> Fixes: 786eb990cfb7 ("drivers/base/node: handle error properly in register_one_node()")
> Signed-off-by: Donet Tom <donettom@...ux.ibm.com>
> ---
>   drivers/base/node.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 1608816de67f..6b6e55a98b79 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -885,7 +885,6 @@ int register_one_node(int nid)
>   	error = register_node(node_devices[nid], nid);
>   	if (error) {
>   		node_devices[nid] = NULL;
> -		kfree(node);
>   		return error;
>   	}
>   

Yes, that matches what other users (staring at mm/memory-tiers.c) do.

I wonder if we should just inline register_node() into register_one_node().

Then it's clearer that we perform a put_device() already in there.

On top of that, we could then just s/register_one_node/register_node/

And then we could do a similar cleanup for unregister_one_node / 
unregister_node where I don't consider the split function really valuable.

-- 
Cheers

David / dhildenb