linux-kernel - Re: [PATCH] s390/net: Mark expected switch fall-throughs

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Date:   Tue, 30 Jul 2019 09:59:02 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Julian Wiedmann <jwi@...ux.ibm.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/net: Mark expected switch fall-throughs

On Mon, Jul 29, 2019 at 07:17:15PM -0500, Gustavo A. R. Silva wrote:
> Mark switch cases where we are expecting to fall through.
> 
> This patch fixes the following warnings (Building: s390):
> 
> drivers/s390/net/ctcm_fsms.c: In function ‘ctcmpc_chx_attnbusy’:
> drivers/s390/net/ctcm_fsms.c:1703:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if (grp->changed_side == 1) {
>       ^
> drivers/s390/net/ctcm_fsms.c:1707:2: note: here
>   case MPCG_STATE_XID0IOWAIX:
>   ^~~~
> 
> drivers/s390/net/ctcm_mpc.c: In function ‘ctc_mpc_alloc_channel’:
> drivers/s390/net/ctcm_mpc.c:358:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if (callback)
>       ^
> drivers/s390/net/ctcm_mpc.c:360:2: note: here
>   case MPCG_STATE_XID0IOWAIT:
>   ^~~~
> 
> drivers/s390/net/ctcm_mpc.c: In function ‘mpc_action_timeout’:
> drivers/s390/net/ctcm_mpc.c:1469:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if ((fsm_getstate(rch->fsm) == CH_XID0_PENDING) &&
>       ^
> drivers/s390/net/ctcm_mpc.c:1472:2: note: here
>   default:
>   ^~~~~~~
> drivers/s390/net/ctcm_mpc.c: In function ‘mpc_send_qllc_discontact’:
> drivers/s390/net/ctcm_mpc.c:2087:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if (grp->estconnfunc) {
>       ^
> drivers/s390/net/ctcm_mpc.c:2092:2: note: here
>   case MPCG_STATE_FLOWC:
>   ^~~~
> 
> drivers/s390/net/qeth_l2_main.c: In function ‘qeth_l2_process_inbound_buffer’:
> drivers/s390/net/qeth_l2_main.c:328:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
>     if (IS_OSN(card)) {
>        ^
> drivers/s390/net/qeth_l2_main.c:337:3: note: here
>    default:
>    ^~~~~~~
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  drivers/s390/net/ctcm_fsms.c    | 1 +
>  drivers/s390/net/ctcm_mpc.c     | 3 +++
>  drivers/s390/net/qeth_l2_main.c | 2 +-
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/s390/net/ctcm_fsms.c b/drivers/s390/net/ctcm_fsms.c
> index 1b4ee570b712..4a8a5373cb35 100644
> --- a/drivers/s390/net/ctcm_fsms.c
> +++ b/drivers/s390/net/ctcm_fsms.c
> @@ -1704,6 +1704,7 @@ static void ctcmpc_chx_attnbusy(fsm_instance *fsm, int event, void *arg)
>  			grp->changed_side = 2;
>  			break;
>  		}
> +		/* Else, fall through */
>  	case MPCG_STATE_XID0IOWAIX:
>  	case MPCG_STATE_XID7INITW:
>  	case MPCG_STATE_XID7INITX:
> diff --git a/drivers/s390/net/ctcm_mpc.c b/drivers/s390/net/ctcm_mpc.c
> index e02f295d38a9..1534420a0243 100644
> --- a/drivers/s390/net/ctcm_mpc.c
> +++ b/drivers/s390/net/ctcm_mpc.c
> @@ -357,6 +357,7 @@ int ctc_mpc_alloc_channel(int port_num, void (*callback)(int, int))
>  		/*fsm_newstate(grp->fsm, MPCG_STATE_XID2INITW);*/
>  		if (callback)
>  			grp->send_qllc_disc = 1;
> +		/* Else, fall through */
>  	case MPCG_STATE_XID0IOWAIT:
>  		fsm_deltimer(&grp->timer);
>  		grp->outstanding_xid2 = 0;
> @@ -1469,6 +1470,7 @@ static void mpc_action_timeout(fsm_instance *fi, int event, void *arg)
>  		if ((fsm_getstate(rch->fsm) == CH_XID0_PENDING) &&
>  		   (fsm_getstate(wch->fsm) == CH_XID0_PENDING))
>  			break;
> +		/* Else, fall through */
>  	default:
>  		fsm_event(grp->fsm, MPCG_EVENT_INOP, dev);
>  	}
> @@ -2089,6 +2091,7 @@ static int mpc_send_qllc_discontact(struct net_device *dev)
>  			grp->estconnfunc = NULL;
>  			break;
>  		}
> +		/* Else, fall through */
>  	case MPCG_STATE_FLOWC:
>  	case MPCG_STATE_READY:
>  		grp->send_qllc_disc = 2;
> diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
> index fd64bc3f4062..cbead3d1b2fd 100644
> --- a/drivers/s390/net/qeth_l2_main.c
> +++ b/drivers/s390/net/qeth_l2_main.c
> @@ -333,7 +333,7 @@ static int qeth_l2_process_inbound_buffer(struct qeth_card *card,
>  				card->osn_info.data_cb(skb);
>  				break;
>  			}
> -			/* else unknown */
> +			/* Else, fall through */
>  		default:
>  			dev_kfree_skb_any(skb);
>  			QETH_CARD_TEXT(card, 3, "inbunkno");
> -- 
> 2.22.0
> 

-- 
Kees Cook