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Date:   Tue, 17 Jan 2023 02:34:26 +0200
From:   Vladimir Oltean <olteanv@gmail.com>
To:     Piergiorgio Beruto <piergiorgio.beruto@gmail.com>
Cc:     Andrew Lunn <andrew@lunn.ch>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Oleksij Rempel <o.rempel@pengutronix.de>,
        mailhol.vincent@wanadoo.fr, sudheer.mogilappagari@intel.com,
        sbhatta@marvell.com, linux-doc@vger.kernel.org,
        wangjie125@huawei.com, corbet@lwn.net, lkp@intel.com,
        gal@nvidia.com, gustavoars@kernel.org, bagasdotme@gmail.com
Subject: Re: [PATCH net-next 1/1] ethtool/plca: fix potential NULL pointer
 access
Message-ID: <20230117003426.pzioywqybaxq4pzm@skbuf>
References: <6bb97c2304d9ab499c2831855f6bf3f6ee2b8676.1673913385.git.piergiorgio.beruto@gmail.com>
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On Tue, Jan 17, 2023 at 12:57:19AM +0100, Piergiorgio Beruto wrote:
> Fix problem found by syzbot dereferencing a device pointer.
> 
> Signed-off-by: Piergiorgio Beruto <piergiorgio.beruto@gmail.com>
> Reported-by: syzbot+8cf35743af243e5f417e@syzkaller.appspotmail.com
> Fixes: 8580e16c28f3 ("net/ethtool: add netlink interface for the PLCA RS")
> ---
>  net/ethtool/plca.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/ethtool/plca.c b/net/ethtool/plca.c
> index be7404dc9ef2..bc3d31f99998 100644
> --- a/net/ethtool/plca.c
> +++ b/net/ethtool/plca.c
> @@ -155,6 +155,8 @@ int ethnl_set_plca_cfg(struct sk_buff *skb, struct genl_info *info)
>  		return ret;
>  
>  	dev = req_info.dev;
> +	if(!dev)
> +		return -ENODEV;

Shouldn't be necessary. The fact that you pass "true" to the
"require_dev" argument of ethnl_parse_header_dev_get() takes care
specifically of that.

Looking at that syzbot report, it looks like you solved it with commit
28dbf774bc87 ("plca.c: fix obvious mistake in checking retval"). Or was
that not the only issue?

>  
>  	rtnl_lock();
>  
> -- 
> 2.37.4
>