[PATCH] drivers/base/node: Fix double free in register_one_node()

[PATCH] drivers/base/node: Fix double free in register_one_node()

[Donet Tom]

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@linux.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;
 	}
 
-- 
2.51.0

Re: [PATCH] drivers/base/node: Fix double free in register_one_node()

[David Hildenbrand]

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@linux.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

Re: [PATCH] drivers/base/node: Fix double free in register_one_node()

[David Hildenbrand]

On 18.09.25 07:55, David Hildenbrand wrote:
> 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@linux.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 forgot

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers

David / dhildenb

Re: [PATCH] drivers/base/node: Fix double free in register_one_node()

[Donet Tom]

On 9/18/25 11:25 AM, David Hildenbrand wrote:
> 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@linux.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.


Sure David, I will work on it and send it as a separate patch.

Re: [PATCH] drivers/base/node: Fix double free in register_one_node()

[Oscar Salvador]

On Thu, Sep 18, 2025 at 07:55:07AM +0200, David Hildenbrand wrote:
> 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.

Yap, that makes sense to me as well.

 

-- 
Oscar Salvador
SUSE Labs

Re: [PATCH] drivers/base/node: Fix double free in register_one_node()

[Oscar Salvador]

On Thu, Sep 18, 2025 at 11:11:44AM +0530, 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@linux.ibm.com>

Acked-by: Oscar Salvador <osalvador@suse.de>

 

-- 
Oscar Salvador
SUSE Labs