Subject: Re: [PATCH v2] powerpc: kernel: legacy_serial: Fix missing of_node_put() in add_legacy_soc_port()

From: Michael Ellerman <[email-masked]>
Date: Mon, 05 Sep 2022 13:25:38 +1000

Liang He <[email-masked]> writes:
> We should call of_node_put() for the reference 'tsi' returned by
> of_get_parent() which will increase the refcount.
>
> Signed-off-by: Liang He <[email-masked]>
> ---
>  changelog:
>
>  v2: use more conservative way to call of_node_put()
>  v1: mov 'of_node_put()' into the 'if' condition
>
>  v1 Link: https://lore.kernel.org/all/[email-masked]/
>
>  arch/powerpc/kernel/legacy_serial.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/legacy_serial.c b/arch/powerpc/kernel/legacy_serial.c
> index f048c424c525..cca72081b864 100644
> --- a/arch/powerpc/kernel/legacy_serial.c
> +++ b/arch/powerpc/kernel/legacy_serial.c
> @@ -166,7 +166,7 @@ static int __init add_legacy_soc_port(struct device_node *np,
>  {
>  	u64 addr;
>  	const __be32 *addrp;
> -	struct device_node *tsi = of_get_parent(np);
> +	struct device_node *tsi;
>  
>  	/* We only support ports that have a clock frequency properly
>  	 * encoded in the device-tree.
> @@ -194,12 +194,17 @@ static int __init add_legacy_soc_port(struct device_node *np,
>  	/* Add port, irq will be dealt with later. We passed a translated
>  	 * IO port value. It will be fixed up later along with the irq
>  	 */
> -	if (of_node_is_type(tsi, "tsi-bridge"))
> +	tsi = of_get_parent(np);
> +	if (of_node_is_type(tsi, "tsi-bridge")) {
> +		of_node_put(tsi);
>  		return add_legacy_port(np, -1, UPIO_TSI, addr, addr,
>  				       0, legacy_port_flags, 0);
> -	else
> +	}
> +	else {
> +		of_node_put(tsi);
>  		return add_legacy_port(np, -1, UPIO_MEM, addr, addr,
>  				       0, legacy_port_flags, 0);
> +	}
>  }

The two legs of the else end up with duplicated code except for a single
parameter to add_legacy_port().

Better would be:

{
	int iotype;
        ...

	tsi = of_get_parent(np);
	if (of_node_is_type(tsi, "tsi-bridge"))
		iotype = UPIO_TSI;
	else
		iotype = UPIO_MEM;

	of_node_put(tsi);
        return add_legacy_port(np, -1, iotype, addr, addr, 0, legacy_port_flags, 0);
}

cheers