[PATCH net 4/5] net/smc: protect connection state transitions in listen work

["D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>]

From: "D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>

Consider the following scenario:

				smc_close_passive_work
smc_listen_out_connected
				lock_sock()
if (state  == SMC_INIT)
				if (state  == SMC_INIT)
					state = SMC_APPCLOSEWAIT1;
	state = SMC_ACTIVE
				release_sock()

This would cause the state machine of the connection to be corrupted.
Also, this issue can occur in smc_listen_out_err().

To solve this problem, we can protect the state transitions under
the lock of sock to avoid collision.

Fixes: 3b2dec2603d5 ("net/smc: restructure client and server code in af_smc")
Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>
---
 net/smc/af_smc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 5ad2a9f..3bb8265 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1926,8 +1926,10 @@ static void smc_listen_out_connected(struct smc_sock *new_smc)
 {
 	struct sock *newsmcsk = &new_smc->sk;
 
+	lock_sock(newsmcsk);
 	if (newsmcsk->sk_state == SMC_INIT)
 		newsmcsk->sk_state = SMC_ACTIVE;
+	release_sock(newsmcsk);
 
 	smc_listen_out(new_smc);
 }
@@ -1939,9 +1941,12 @@ static void smc_listen_out_err(struct smc_sock *new_smc)
 	struct net *net = sock_net(newsmcsk);
 
 	this_cpu_inc(net->smc.smc_stats->srv_hshake_err_cnt);
+
+	lock_sock(newsmcsk);
 	if (newsmcsk->sk_state == SMC_INIT)
 		sock_put(&new_smc->sk); /* passive closing */
 	newsmcsk->sk_state = SMC_CLOSED;
+	release_sock(newsmcsk);
 
 	smc_listen_out(new_smc);
 }
-- 
1.8.3.1