netdev - Re: [PATCH net 1/5] net/smc: fix dangling sock under state SMC

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Date: Wed, 11 Oct 2023 22:31:34 +0200
From: Wenjia Zhang <wenjia@...ux.ibm.com>
To: "D. Wythe" <alibuda@...ux.alibaba.com>, kgraul@...ux.ibm.com,
        jaka@...ux.ibm.com, wintera@...ux.ibm.com
Cc: kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net 1/5] net/smc: fix dangling sock under state
 SMC_APPFINCLOSEWAIT



On 11.10.23 09:33, D. Wythe wrote:
> From: "D. Wythe" <alibuda@...ux.alibaba.com>
> 
> Considering scenario:
> 
> 				smc_cdc_rx_handler_rwwi
> __smc_release
> 				sock_set_flag
> smc_close_active()
> sock_set_flag
> 
> __set_bit(DEAD)			__set_bit(DONE)
> 
> Dues to __set_bit is not atomic, the DEAD or DONE might be lost.
> if the DEAD flag lost, the state SMC_CLOSED  will be never be reached
> in smc_close_passive_work:
> 
> if (sock_flag(sk, SOCK_DEAD) &&
> 	smc_close_sent_any_close(conn)) {
> 	sk->sk_state = SMC_CLOSED;
> } else {
> 	/* just shutdown, but not yet closed locally */
> 	sk->sk_state = SMC_APPFINCLOSEWAIT;
> }
> 
> Replace sock_set_flags or __set_bit to set_bit will fix this problem.
> Since set_bit is atomic.
> 
I didn't really understand the scenario. What is 
smc_cdc_rx_handler_rwwi()? What does it do? Don't it get the lock during 
the runtime?

> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
> ---
>   net/smc/af_smc.c    | 4 ++--
>   net/smc/smc.h       | 5 +++++
>   net/smc/smc_cdc.c   | 2 +-
>   net/smc/smc_close.c | 2 +-
>   4 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
> index bacdd97..5ad2a9f 100644
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -275,7 +275,7 @@ static int __smc_release(struct smc_sock *smc)
>   
>   	if (!smc->use_fallback) {
>   		rc = smc_close_active(smc);
> -		sock_set_flag(sk, SOCK_DEAD);
> +		smc_sock_set_flag(sk, SOCK_DEAD);
>   		sk->sk_shutdown |= SHUTDOWN_MASK;
>   	} else {
>   		if (sk->sk_state != SMC_CLOSED) {
> @@ -1742,7 +1742,7 @@ static int smc_clcsock_accept(struct smc_sock *lsmc, struct smc_sock **new_smc)
>   		if (new_clcsock)
>   			sock_release(new_clcsock);
>   		new_sk->sk_state = SMC_CLOSED;
> -		sock_set_flag(new_sk, SOCK_DEAD);
> +		smc_sock_set_flag(new_sk, SOCK_DEAD);
>   		sock_put(new_sk); /* final */
>   		*new_smc = NULL;
>   		goto out;
> diff --git a/net/smc/smc.h b/net/smc/smc.h
> index 24745fd..e377980 100644
> --- a/net/smc/smc.h
> +++ b/net/smc/smc.h
> @@ -377,4 +377,9 @@ void smc_fill_gid_list(struct smc_link_group *lgr,
>   int smc_nl_enable_hs_limitation(struct sk_buff *skb, struct genl_info *info);
>   int smc_nl_disable_hs_limitation(struct sk_buff *skb, struct genl_info *info);
>   
> +static inline void smc_sock_set_flag(struct sock *sk, enum sock_flags flag)
> +{
> +	set_bit(flag, &sk->sk_flags);
> +}
> +
>   #endif	/* __SMC_H */
> diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
> index 89105e9..01bdb79 100644
> --- a/net/smc/smc_cdc.c
> +++ b/net/smc/smc_cdc.c
> @@ -385,7 +385,7 @@ static void smc_cdc_msg_recv_action(struct smc_sock *smc,
>   		smc->sk.sk_shutdown |= RCV_SHUTDOWN;
>   		if (smc->clcsock && smc->clcsock->sk)
>   			smc->clcsock->sk->sk_shutdown |= RCV_SHUTDOWN;
> -		sock_set_flag(&smc->sk, SOCK_DONE);
> +		smc_sock_set_flag(&smc->sk, SOCK_DONE);
>   		sock_hold(&smc->sk); /* sock_put in close_work */
>   		if (!queue_work(smc_close_wq, &conn->close_work))
>   			sock_put(&smc->sk);
> diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c
> index dbdf03e..449ef45 100644
> --- a/net/smc/smc_close.c
> +++ b/net/smc/smc_close.c
> @@ -173,7 +173,7 @@ void smc_close_active_abort(struct smc_sock *smc)
>   		break;
>   	}
>   
> -	sock_set_flag(sk, SOCK_DEAD);
> +	smc_sock_set_flag(sk, SOCK_DEAD);
>   	sk->sk_state_change(sk);
>   
>   	if (release_clcsock) {