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Date:   Wed, 20 Feb 2019 16:57:52 +0200
From:   Rémi Denis-Courmont <remi@...lab.net>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Remi Denis-Courmont <courmisch@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Nathan Chancellor <natechancellor@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] phonet: fix building with clang

Le tiistaina 19. helmikuuta 2019, 23.53.50 EET Arnd Bergmann a écrit :
> clang warns about overflowing the data[] member in the struct pnpipehdr:
> 
> net/phonet/pep.c:295:8: warning: array index 4 is past the end of the array
> (which contains 1 element) [-Warray-bounds] if (hdr->data[4] ==
> PEP_IND_READY)
>                             ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
> 
> Using a flexible array member at the end of the struct avoids the
> warning, but since we cannot have a flexible array member inside
> of the union, each index now has to be moved back by one, which
> makes it a little uglier.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Rémi Denis-Courmont <remi@...lab.net>

> ---
>  include/net/phonet/pep.h |  5 +++--
>  net/phonet/pep.c         | 32 ++++++++++++++++----------------
>  2 files changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/include/net/phonet/pep.h b/include/net/phonet/pep.h
> index b669fe6dbc3b..98f31c7ea23d 100644
> --- a/include/net/phonet/pep.h
> +++ b/include/net/phonet/pep.h
> @@ -63,10 +63,11 @@ struct pnpipehdr {
>  		u8		state_after_reset;	/* reset request */
>  		u8		error_code;		/* any response */
>  		u8		pep_type;		/* status indication */
> -		u8		data[1];
> +		u8		data0;			/* anything else */
>  	};
> +	u8			data[];
>  };
> -#define other_pep_type		data[1]
> +#define other_pep_type		data[0]
> 
>  static inline struct pnpipehdr *pnp_hdr(struct sk_buff *skb)
>  {
> diff --git a/net/phonet/pep.c b/net/phonet/pep.c
> index 9fc76b19cd3c..db3473540303 100644
> --- a/net/phonet/pep.c
> +++ b/net/phonet/pep.c
> @@ -132,7 +132,7 @@ static int pep_indicate(struct sock *sk, u8 id, u8 code,
> ph->utid = 0;
>  	ph->message_id = id;
>  	ph->pipe_handle = pn->pipe_handle;
> -	ph->data[0] = code;
> +	ph->error_code = code;
>  	return pn_skb_send(sk, skb, NULL);
>  }
> 
> @@ -153,7 +153,7 @@ static int pipe_handler_request(struct sock *sk, u8 id,
> u8 code, ph->utid = id; /* whatever */
>  	ph->message_id = id;
>  	ph->pipe_handle = pn->pipe_handle;
> -	ph->data[0] = code;
> +	ph->error_code = code;
>  	return pn_skb_send(sk, skb, NULL);
>  }
> 
> @@ -208,7 +208,7 @@ static int pep_ctrlreq_error(struct sock *sk, struct
> sk_buff *oskb, u8 code, struct pnpipehdr *ph;
>  	struct sockaddr_pn dst;
>  	u8 data[4] = {
> -		oph->data[0], /* PEP type */
> +		oph->pep_type, /* PEP type */
>  		code, /* error code, at an unusual offset */
>  		PAD, PAD,
>  	};
> @@ -221,7 +221,7 @@ static int pep_ctrlreq_error(struct sock *sk, struct
> sk_buff *oskb, u8 code, ph->utid = oph->utid;
>  	ph->message_id = PNS_PEP_CTRL_RESP;
>  	ph->pipe_handle = oph->pipe_handle;
> -	ph->data[0] = oph->data[1]; /* CTRL id */
> +	ph->data0 = oph->data[0]; /* CTRL id */
> 
>  	pn_skb_get_src_sockaddr(oskb, &dst);
>  	return pn_skb_send(sk, skb, &dst);
> @@ -272,17 +272,17 @@ static int pipe_rcv_status(struct sock *sk, struct
> sk_buff *skb) return -EINVAL;
> 
>  	hdr = pnp_hdr(skb);
> -	if (hdr->data[0] != PN_PEP_TYPE_COMMON) {
> +	if (hdr->pep_type != PN_PEP_TYPE_COMMON) {
>  		net_dbg_ratelimited("Phonet unknown PEP type: %u\n",
> -				    (unsigned int)hdr->data[0]);
> +				    (unsigned int)hdr->pep_type);
>  		return -EOPNOTSUPP;
>  	}
> 
> -	switch (hdr->data[1]) {
> +	switch (hdr->data[0]) {
>  	case PN_PEP_IND_FLOW_CONTROL:
>  		switch (pn->tx_fc) {
>  		case PN_LEGACY_FLOW_CONTROL:
> -			switch (hdr->data[4]) {
> +			switch (hdr->data[3]) {
>  			case PEP_IND_BUSY:
>  				atomic_set(&pn->tx_credits, 0);
>  				break;
> @@ -292,7 +292,7 @@ static int pipe_rcv_status(struct sock *sk, struct
> sk_buff *skb) }
>  			break;
>  		case PN_ONE_CREDIT_FLOW_CONTROL:
> -			if (hdr->data[4] == PEP_IND_READY)
> +			if (hdr->data[3] == PEP_IND_READY)
>  				atomic_set(&pn->tx_credits, wake = 1);
>  			break;
>  		}
> @@ -301,12 +301,12 @@ static int pipe_rcv_status(struct sock *sk, struct
> sk_buff *skb) case PN_PEP_IND_ID_MCFC_GRANT_CREDITS:
>  		if (pn->tx_fc != PN_MULTI_CREDIT_FLOW_CONTROL)
>  			break;
> -		atomic_add(wake = hdr->data[4], &pn->tx_credits);
> +		atomic_add(wake = hdr->data[3], &pn->tx_credits);
>  		break;
> 
>  	default:
>  		net_dbg_ratelimited("Phonet unknown PEP indication: %u\n",
> -				    (unsigned int)hdr->data[1]);
> +				    (unsigned int)hdr->data[0]);
>  		return -EOPNOTSUPP;
>  	}
>  	if (wake)
> @@ -318,7 +318,7 @@ static int pipe_rcv_created(struct sock *sk, struct
> sk_buff *skb) {
>  	struct pep_sock *pn = pep_sk(sk);
>  	struct pnpipehdr *hdr = pnp_hdr(skb);
> -	u8 n_sb = hdr->data[0];
> +	u8 n_sb = hdr->data0;
> 
>  	pn->rx_fc = pn->tx_fc = PN_LEGACY_FLOW_CONTROL;
>  	__skb_pull(skb, sizeof(*hdr));
> @@ -506,7 +506,7 @@ static int pep_connresp_rcv(struct sock *sk, struct
> sk_buff *skb) return -ECONNREFUSED;
> 
>  	/* Parse sub-blocks */
> -	n_sb = hdr->data[4];
> +	n_sb = hdr->data[3];
>  	while (n_sb > 0) {
>  		u8 type, buf[6], len = sizeof(buf);
>  		const u8 *data = pep_get_sb(skb, &type, &len, buf);
> @@ -739,7 +739,7 @@ static int pipe_do_remove(struct sock *sk)
>  	ph->utid = 0;
>  	ph->message_id = PNS_PIPE_REMOVE_REQ;
>  	ph->pipe_handle = pn->pipe_handle;
> -	ph->data[0] = PAD;
> +	ph->data0 = PAD;
>  	return pn_skb_send(sk, skb, NULL);
>  }
> 
> @@ -817,7 +817,7 @@ static struct sock *pep_sock_accept(struct sock *sk, int
> flags, int *errp, peer_type = hdr->other_pep_type << 8;
> 
>  	/* Parse sub-blocks (options) */
> -	n_sb = hdr->data[4];
> +	n_sb = hdr->data[3];
>  	while (n_sb > 0) {
>  		u8 type, buf[1], len = sizeof(buf);
>  		const u8 *data = pep_get_sb(skb, &type, &len, buf);
> @@ -1109,7 +1109,7 @@ static int pipe_skb_send(struct sock *sk, struct
> sk_buff *skb) ph->utid = 0;
>  	if (pn->aligned) {
>  		ph->message_id = PNS_PIPE_ALIGNED_DATA;
> -		ph->data[0] = 0; /* padding */
> +		ph->data0 = 0; /* padding */
>  	} else
>  		ph->message_id = PNS_PIPE_DATA;
>  	ph->pipe_handle = pn->pipe_handle;


-- 
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