Re: [PATCH net-next 12/14] net/smc: annotate data-races around smc sysctls

[Dust Li <dust.li@linux.alibaba.com>]

On 2026-11-09 10:52:11, Jiayuan Chen wrote:
>autocorking_size, smcr_buf_type, smcr_max_links_per_lgr,
>smcr_max_conns_per_lgr and limit_smc_hs are read without any lock while
>their sysctl handlers update them with WRITE_ONCE(), and the SMC netlink
>handlers toggle limit_smc_hs with plain writes. Add READ_ONCE() to the
>readers and WRITE_ONCE() to those handlers.
>
>Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Acked-by: Dust Li <dust.li@linux.alibaba.com>

Best regards,
Dust

>---
> net/smc/af_smc.c   | 8 ++++----
> net/smc/smc_clc.c  | 8 ++++----
> net/smc/smc_core.c | 2 +-
> net/smc/smc_tx.c   | 2 +-
> 4 files changed, 10 insertions(+), 10 deletions(-)
>
>diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>index d10244af5bd29..9a657172be8f9 100644
>--- a/net/smc/af_smc.c
>+++ b/net/smc/af_smc.c
>@@ -88,7 +88,7 @@ int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct netlink_callback *cb)
> 		return -ENOMEM;
> 
> 	if (nla_put_u8(skb, SMC_NLA_HS_LIMITATION_ENABLED,
>-		       sock_net(skb->sk)->smc.limit_smc_hs))
>+		       READ_ONCE(sock_net(skb->sk)->smc.limit_smc_hs)))
> 		goto err;
> 
> 	genlmsg_end(skb, hdr);
>@@ -102,13 +102,13 @@ int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct netlink_callback *cb)
> 
> int smc_nl_enable_hs_limitation(struct sk_buff *skb, struct genl_info *info)
> {
>-	sock_net(skb->sk)->smc.limit_smc_hs = true;
>+	WRITE_ONCE(sock_net(skb->sk)->smc.limit_smc_hs, true);
> 	return 0;
> }
> 
> int smc_nl_disable_hs_limitation(struct sk_buff *skb, struct genl_info *info)
> {
>-	sock_net(skb->sk)->smc.limit_smc_hs = false;
>+	WRITE_ONCE(sock_net(skb->sk)->smc.limit_smc_hs, false);
> 	return 0;
> }
> 
>@@ -411,7 +411,7 @@ void smc_sk_init(struct net *net, struct sock *sk, int protocol)
> 	spin_lock_init(&smc->conn.send_lock);
> 	mutex_init(&smc->clcsock_release_lock);
> 	smc_init_saved_callbacks(smc);
>-	smc->limit_smc_hs = net->smc.limit_smc_hs;
>+	smc->limit_smc_hs = READ_ONCE(net->smc.limit_smc_hs);
> 	smc->use_fallback = false; /* assume rdma capability first */
> 	smc->fallback_rsn = 0;
> 	smc_close_init(smc);
>diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
>index 014d527d5462d..df0afeef67cbd 100644
>--- a/net/smc/smc_clc.c
>+++ b/net/smc/smc_clc.c
>@@ -990,8 +990,8 @@ int smc_clc_send_proposal(struct smc_sock *smc, struct smc_init_info *ini)
> 	}
> 	if (smcr_indicated(ini->smc_type_v2)) {
> 		memcpy(v2_ext->roce, ini->smcrv2.ib_gid_v2, SMC_GID_SIZE);
>-		v2_ext->max_conns = net->smc.sysctl_max_conns_per_lgr;
>-		v2_ext->max_links = net->smc.sysctl_max_links_per_lgr;
>+		v2_ext->max_conns = READ_ONCE(net->smc.sysctl_max_conns_per_lgr);
>+		v2_ext->max_links = READ_ONCE(net->smc.sysctl_max_links_per_lgr);
> 	}
> 
> 	pclc_base->hdr.length = htons(plen);
>@@ -1272,12 +1272,12 @@ int smc_clc_srv_v2x_features_validate(struct smc_sock *smc,
> 
> 	if (ini->smcr_version & SMC_V2) {
> 		ini->max_conns = min_t(u8, pclc_v2_ext->max_conns,
>-				       net->smc.sysctl_max_conns_per_lgr);
>+				       READ_ONCE(net->smc.sysctl_max_conns_per_lgr));
> 		if (ini->max_conns < SMC_CONN_PER_LGR_MIN)
> 			return SMC_CLC_DECL_MAXCONNERR;
> 
> 		ini->max_links = min_t(u8, pclc_v2_ext->max_links,
>-				       net->smc.sysctl_max_links_per_lgr);
>+				       READ_ONCE(net->smc.sysctl_max_links_per_lgr));
> 		if (ini->max_links < SMC_LINKS_ADD_LNK_MIN)
> 			return SMC_CLC_DECL_MAXLINKERR;
> 	}
>diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
>index 6021322253e93..3d338019a1b8b 100644
>--- a/net/smc/smc_core.c
>+++ b/net/smc/smc_core.c
>@@ -990,7 +990,7 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini)
> 		lgr->net = smc_ib_net(lnk->smcibdev);
> 		lgr_list = &smc_lgr_list.list;
> 		lgr_lock = &smc_lgr_list.lock;
>-		lgr->buf_type = lgr->net->smc.sysctl_smcr_buf_type;
>+		lgr->buf_type = READ_ONCE(lgr->net->smc.sysctl_smcr_buf_type);
> 		atomic_inc(&lgr_cnt);
> 	}
> 	smc->conn.lgr = lgr;
>diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
>index 0f0c6df3bf2ce..30bffe79d06a3 100644
>--- a/net/smc/smc_tx.c
>+++ b/net/smc/smc_tx.c
>@@ -148,7 +148,7 @@ static bool smc_should_autocork(struct smc_sock *smc)
> 	int corking_size;
> 
> 	corking_size = min_t(unsigned int, conn->sndbuf_desc->len >> 1,
>-			     sock_net(&smc->sk)->smc.sysctl_autocorking_size);
>+			     READ_ONCE(sock_net(&smc->sk)->smc.sysctl_autocorking_size));
> 
> 	if (atomic_read(&conn->cdc_pend_tx_wr) == 0 ||
> 	    smc_tx_prepared_sends(conn) > corking_size)
>-- 
>2.43.0