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

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Date: Wed, 11 Oct 2023 22:00:09 +0800
From: Dust Li <dust.li@...ux.alibaba.com>
To: "D. Wythe" <alibuda@...ux.alibaba.com>, kgraul@...ux.ibm.com,
	wenjia@...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 Wed, Oct 11, 2023 at 03:33:16PM +0800, 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)

If I understand correctly, both operations should hold sock_lock,
that means thay should not race, have I missed something ?

>
>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.
>

You should add a fixes tag.
>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) {
>-- 
>1.8.3.1