Re: [PATCH net-next 1/1] ethtool/plca: fix potential NULL pointer access

[Vladimir Oltean]

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@xxxxxxxxx>
> Reported-by: syzbot+8cf35743af243e5f417e@xxxxxxxxxxxxxxxxxxxxxxxxx
> 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
>