linux-kernel - Re: [PATCH V3] net: dsa: Add of_node_put() before break and return statements

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Message-ID: <20200824133515.j6ujfm2tl2hqjo5u@skbuf>
Date:   Mon, 24 Aug 2020 16:35:15 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Sumera Priyadarsini <sylphrenadin@...il.com>
Cc:     davem@...emloft.net, Julia.Lawall@...6.fr, andrew@...n.ch,
        sean.wang@...iatek.com, vivien.didelot@...il.com,
        f.fainelli@...il.com, kuba@...nel.org, matthias.bgg@...il.com,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] net: dsa: Add of_node_put() before break and return
 statements

On Mon, Aug 24, 2020 at 01:00:54AM +0530, Sumera Priyadarsini wrote:
> Every iteration of for_each_child_of_node() decrements
> the reference count of the previous node, however when control
> is transferred from the middle of the loop, as in the case of
> a return or break or goto, there is no decrement thus ultimately
> resulting in a memory leak.
> 
> Fix a potential memory leak in mt7530.c by inserting of_node_put()
> before the break and return statements.
> 
> Issue found with Coccinelle.
> 
> ---
> Changes in v2:
> 	Add another of_node_put() in for_each_child_of_node() as pointed
> out by Andrew.
> 
> Changes in v3:
> 	- Correct syntax errors
> 	- Modify commit message
> 
> ---
> 
> Signed-off-by: Sumera Priyadarsini <sylphrenadin@...il.com>
> 
> Signed-off-by: Sumera Priyadarsini <sylphrenadin@...il.com>
> ---

If you need to resend anyway, can we please have a proper commit prefix?
A patch on mt7530.c shouldn't be "net: dsa: " but "net: dsa: mt7530: "
as "git log" will tell you. The difference is relevant because "net:
dsa: " typically refers to the generic code in net/dsa/.

>  drivers/net/dsa/mt7530.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> index 8dcb8a49ab67..4b4701c69fe1 100644
> --- a/drivers/net/dsa/mt7530.c
> +++ b/drivers/net/dsa/mt7530.c
> @@ -1326,14 +1326,17 @@ mt7530_setup(struct dsa_switch *ds)
>  
>  			if (phy_node->parent == priv->dev->of_node->parent) {
>  				ret = of_get_phy_mode(mac_np, &interface);
> -				if (ret && ret != -ENODEV)
> +				if (ret && ret != -ENODEV) {
> +					of_node_put(mac_np);
>  					return ret;
> +				}
>  				id = of_mdio_parse_addr(ds->dev, phy_node);
>  				if (id == 0)
>  					priv->p5_intf_sel = P5_INTF_SEL_PHY_P0;
>  				if (id == 4)
>  					priv->p5_intf_sel = P5_INTF_SEL_PHY_P4;
>  			}
> +			of_node_put(mac_np);
>  			of_node_put(phy_node);
>  			break;
>  		}
> -- 
> 2.17.1
> 

Thanks,
-Vladimir