linux-kernel - Re: [PATCH] net: ethtool: fix unheld rtnl lock

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Message-ID: <7eed6937-bb9e-4ab9-9df3-acf8cb9083ab@intel.com>
Date: Mon, 26 Aug 2024 15:30:36 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Diogo Jahchan Koike <djahchankoike@...il.com>
CC: <edumazet@...gle.com>, <kuba@...nel.org>, <davem@...emloft.net>,
	<pabeni@...hat.com>, <kory.maincent@...tlin.com>, <o.rempel@...gutronix.de>,
	<maxime.chevallier@...tlin.com>, <andrew@...n.ch>,
	<christophe.leroy@...roup.eu>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-kernel-mentees@...ts.linuxfoundation.org>,
	<syzkaller-bugs@...glegroups.com>,
	<syzbot+ec369e6d58e210135f71@...kaller.appspotmail.com>
Subject: Re: [PATCH] net: ethtool: fix unheld rtnl lock

On 8/26/24 15:06, Diogo Jahchan Koike wrote:
> ethnl_req_get_phydev should be called with rtnl lock
> held.

Next time please make use of more columns in commit message (75).

> 
> Reported-by: syzbot+ec369e6d58e210135f71@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=ec369e6d58e210135f71
> Fixes: 31748765bed3 ("net: ethtool: pse-pd: Target the command to the requested PHY")
> Signed-off-by: Diogo Jahchan Koike <djahchankoike@...il.com>
> ---
>   net/ethtool/pse-pd.c | 18 +++++++++++++-----
>   1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/net/ethtool/pse-pd.c b/net/ethtool/pse-pd.c
> index 507cb21d6bf0..290edbfd47d2 100644
> --- a/net/ethtool/pse-pd.c
> +++ b/net/ethtool/pse-pd.c
> @@ -226,17 +226,21 @@ ethnl_set_pse_validate(struct ethnl_req_info *req_info, struct genl_info *info)
>   {
>   	struct nlattr **tb = info->attrs;
>   	struct phy_device *phydev;
> +	int ret = 1;
>   
> +	rtnl_lock();
>   	phydev = ethnl_req_get_phydev(req_info, tb[ETHTOOL_A_PSE_HEADER],
>   				      info->extack);

Fix looks fine, thanks, I will however unlock just after
ethnl_req_get_phydev() call.
Then all ret code logic touches could be omitted.

>   	if (IS_ERR_OR_NULL(phydev)) {
>   		NL_SET_ERR_MSG(info->extack, "No PHY is attached");
> -		return -EOPNOTSUPP;
> +		ret = -EOPNOTSUPP;
> +		goto out;
>   	}
>   
>   	if (!phydev->psec) {
>   		NL_SET_ERR_MSG(info->extack, "No PSE is attached");
> -		return -EOPNOTSUPP;
> +		ret = -EOPNOTSUPP;
> +		goto out;
>   	}
>   
>   	if (tb[ETHTOOL_A_PODL_PSE_ADMIN_CONTROL] &&
> @@ -244,17 +248,21 @@ ethnl_set_pse_validate(struct ethnl_req_info *req_info, struct genl_info *info)
>   		NL_SET_ERR_MSG_ATTR(info->extack,
>   				    tb[ETHTOOL_A_PODL_PSE_ADMIN_CONTROL],
>   				    "setting PoDL PSE admin control not supported");
> -		return -EOPNOTSUPP;
> +		ret = -EOPNOTSUPP;
> +		goto out;
>   	}
>   	if (tb[ETHTOOL_A_C33_PSE_ADMIN_CONTROL] &&
>   	    !pse_has_c33(phydev->psec)) {
>   		NL_SET_ERR_MSG_ATTR(info->extack,
>   				    tb[ETHTOOL_A_C33_PSE_ADMIN_CONTROL],
>   				    "setting C33 PSE admin control not supported");
> -		return -EOPNOTSUPP;
> +		ret = -EOPNOTSUPP;
> +		goto out;
>   	}
>   
> -	return 1;
> +out:
> +	rtnl_unlock();
> +	return ret;
>   }
>   
>   static int