netdev - Re: [PATCH net] net: genl: fix error path memory leak in policy dumping

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Date:   Mon, 15 Aug 2022 18:08:58 -0300
From:   Rafael Soares <rafaelmendsr@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
        pabeni@...hat.com, johannes.berg@...el.com,
        syzbot+dc54d9ba8153b216cae0@...kaller.appspotmail.com
Subject: Re: [PATCH net] net: genl: fix error path memory leak in policy
 dumping

On Mon, Aug 15, 2022 at 11:20:21AM -0700, Jakub Kicinski wrote:
> If construction of the array of policies fails when recording
> non-first policy we need to unwind.
> 
> Reported-by: syzbot+dc54d9ba8153b216cae0@...kaller.appspotmail.com
> Fixes: 50a896cf2d6f ("genetlink: properly support per-op policy dumping")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
>  net/netlink/genetlink.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
> index 1afca2a6c2ac..57010927e20a 100644
> --- a/net/netlink/genetlink.c
> +++ b/net/netlink/genetlink.c
> @@ -1174,13 +1174,17 @@ static int ctrl_dumppolicy_start(struct netlink_callback *cb)
>  							     op.policy,
>  							     op.maxattr);
>  			if (err)
> -				return err;
> +				goto err_free_state;

There's another call to netlink_policy_dump_add_policy() right above
this one. The patch I posted to syzkaller frees the memory inside
netlink_policy_dump_add_policy() and the result was OK.

>  		}
>  	}
>  
>  	if (!ctx->state)
>  		return -ENODATA;
>  	return 0;
> +
> +err_free_state:
> +	netlink_policy_dump_free(ctx->state);
> +	return err;
>  }
>  
>  static void *ctrl_dumppolicy_prep(struct sk_buff *skb,
> -- 
> 2.37.2
>