netdev - Re: [PATCH net-next v6 1/2] nfc: llcp_core: Hold a ref to llcp_local->dev when holding a ref to llcp

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Message-ID: <6160aa1e-5f77-4d7d-aafd-e1ac7606bf06@linaro.org>
Date: Mon, 18 Dec 2023 10:39:00 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Siddh Raman Pant <code@...dh.me>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Suman Ghosh <sumang@...vell.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot+bbe84a4010eeea00982d@...kaller.appspotmail.com
Subject: Re: [PATCH net-next v6 1/2] nfc: llcp_core: Hold a ref to
 llcp_local->dev when holding a ref to llcp_local

On 17/12/2023 14:11, Siddh Raman Pant wrote:
>  static struct nfc_llcp_sock *nfc_llcp_sock_get(struct nfc_llcp_local *local,
> @@ -959,8 +974,18 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local,
>  	}
>  
>  	new_sock = nfc_llcp_sock(new_sk);
> -	new_sock->dev = local->dev;
> +
>  	new_sock->local = nfc_llcp_local_get(local);
> +	if (!new_sock->local) {
> +		reason = LLCP_DM_REJ;
> +		release_sock(&sock->sk);
> +		sock_put(&sock->sk);
> +		sock_put(&new_sock->sk);

Why is this needed? Which part earlier gets the reference?

> +		nfc_llcp_sock_free(new_sock);

This order is still wrong. Unwinding is almost always done in reversed
order, for good reasons. Why do you unwind in other order?

> +		goto fail;
> +	}
> +
> +	new_sock->dev = local->dev;
>  	new_sock->rw = sock->rw;
>  	new_sock->miux = sock->miux;
Best regards,
Krzysztof