net/smc: fix listen processing for SMC-Rv2

In the process of checking whether RDMAv2 is available, the current
implementation first sets ini->smcrv2.ib_dev_v2, and then allocates
smc buf desc, but the latter may fail. Unfortunately, the caller
will only check the former. In this case, a NULL pointer reference
will occur in smc_clc_send_confirm_accept() when accessing
conn->rmb_desc.

This patch does two things:
1. Use the return code to determine whether V2 is available.
2. If the return code is NODEV, continue to check whether V1 is
available.

Fixes: e49300a ("net/smc: add listen processing for SMC-Rv2")
Signed-off-by: liuyacan <liuyacan@corp.netease.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: liuyacan

net/smc/af_smc.c

@@ -2093,13 +2093,13 @@ static int smc_listen_rdma_reg(struct smc_sock *new_smc, bool local_first)
 	return 0;
 }
 
-static void smc_find_rdma_v2_device_serv(struct smc_sock *new_smc,
-					 struct smc_clc_msg_proposal *pclc,
-					 struct smc_init_info *ini)
+static int smc_find_rdma_v2_device_serv(struct smc_sock *new_smc,
+					struct smc_clc_msg_proposal *pclc,
+					struct smc_init_info *ini)
 {
 	struct smc_clc_v2_extension *smc_v2_ext;
 	u8 smcr_version;
-	int rc;
+	int rc = 0;
 
 	if (!(ini->smcr_version & SMC_V2) || !smcr_indicated(ini->smc_type_v2))
 		goto not_found;
@@ -2117,26 +2117,31 @@ static void smc_find_rdma_v2_device_serv(struct smc_sock *new_smc,
 	ini->smcrv2.saddr = new_smc->clcsock->sk->sk_rcv_saddr;
 	ini->smcrv2.daddr = smc_ib_gid_to_ipv4(smc_v2_ext->roce);
 	rc = smc_find_rdma_device(new_smc, ini);
-	if (rc) {
-		smc_find_ism_store_rc(rc, ini);
+	if (rc)
 		goto not_found;
-	}
+
 	if (!ini->smcrv2.uses_gateway)
 		memcpy(ini->smcrv2.nexthop_mac, pclc->lcl.mac, ETH_ALEN);
 
 	smcr_version = ini->smcr_version;
 	ini->smcr_version = SMC_V2;
 	rc = smc_listen_rdma_init(new_smc, ini);
-	if (!rc)
-		rc = smc_listen_rdma_reg(new_smc, ini->first_contact_local);
-	if (!rc)
-		return;
-	ini->smcr_version = smcr_version;
-	smc_find_ism_store_rc(rc, ini);
+	if (rc) {
+		ini->smcr_version = smcr_version;
+		goto not_found;
+	}
+	rc = smc_listen_rdma_reg(new_smc, ini->first_contact_local);
+	if (rc) {
+		ini->smcr_version = smcr_version;
+		goto not_found;
+	}
+	return 0;
 
 not_found:
+	rc = rc ?: SMC_CLC_DECL_NOSMCDEV;
 	ini->smcr_version &= ~SMC_V2;
 	ini->check_smcrv2 = false;
+	return rc;
 }
 
 static int smc_find_rdma_v1_device_serv(struct smc_sock *new_smc,
@@ -2169,6 +2174,7 @@ static int smc_listen_find_device(struct smc_sock *new_smc,
 				  struct smc_init_info *ini)
 {
 	int prfx_rc;
+	int rc;
 
 	/* check for ISM device matching V2 proposed device */
 	smc_find_ism_v2_device_serv(new_smc, pclc, ini);
@@ -2196,14 +2202,18 @@ static int smc_listen_find_device(struct smc_sock *new_smc,
 		return ini->rc ?: SMC_CLC_DECL_NOSMCDDEV;
 
 	/* check if RDMA V2 is available */
-	smc_find_rdma_v2_device_serv(new_smc, pclc, ini);
-	if (ini->smcrv2.ib_dev_v2)
+	rc = smc_find_rdma_v2_device_serv(new_smc, pclc, ini);
+	if (!rc)
 		return 0;
 
+	/* skip V1 check if V2 is unavailable for non-Device reason */
+	if (rc != SMC_CLC_DECL_NOSMCDEV &&
+	    rc != SMC_CLC_DECL_NOSMCRDEV &&
+	    rc != SMC_CLC_DECL_NOSMCDDEV)
+		return rc;
+
 	/* check if RDMA V1 is available */
 	if (!prfx_rc) {
-		int rc;
-
 		rc = smc_find_rdma_v1_device_serv(new_smc, pclc, ini);
 		smc_find_ism_store_rc(rc, ini);
 		return (!rc) ? 0 : ini->rc;