Re: [PATCH] of: overlay: fix memory leak in add_changeset_node()

[Frank Rowand]

On 11/18/22 04:53, Zeng Heng wrote:
> In of_changeset_action(), we have called of_node_get() to increase
> refcount of a node.
> 
> Therefore, when tchild (duplicated by __of_node_dup()) is done,
> of_node_put() needs to call and release the device_node.
> 
> Otherwise, there are some memory leak reported about the node:
> 
> unreferenced object 0xffff88810cd1e800 (size 256):
>   backtrace:
>     kmalloc_trace
>     __of_node_dup
>     add_changeset_node (inlined)
>     build_changeset_next_level
> 
> unreferenced object 0xffff888113721240 (size 16):
>   backtrace:
>     __kmalloc_node_track_caller
>     kstrdup
>     __of_node_dup
>     add_changeset_node (inlined)
>     build_changeset_next_level
> 
> unreferenced object 0xffff88810a38d400 (size 128):
>   backtrace:
>     kmalloc_trace
>     __of_prop_dup
>     add_changeset_property
>     build_changeset_next_level
> 
> Fixes: 7518b5890d8a ("of/overlay: Introduce DT overlay support")
> Signed-off-by: Zeng Heng <zengheng4@xxxxxxxxxx>
> ---
>  drivers/of/overlay.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index bd8ff4df723d..a5189a0ec0a3 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -436,8 +436,10 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
>  		of_node_set_flag(tchild, OF_OVERLAY);
>  
>  		ret = of_changeset_attach_node(&ovcs->cset, tchild);
> -		if (ret)
> +		if (ret) {
> +			of_node_put(tchild);
>  			return ret;
> +		}

By visual inspection of the code (Linux 6.1-rc1), this does not appear to be
correct.  For the only case where of_changeset_action(),
called by of_changeset_attach_node(), returns an error, of_node_get() has not
yet occurred on tchild.

>  
>  		target_child.np = tchild;
>  		target_child.in_livetree = false;

For which version of Linux were the memory leaks detected?  Were any additional
patches applied?

-Frank