net/smc: prevent races between smc_lgr_terminate() and smc_conn_free()

[ Upstream commit 77f838ace755d2f466536c44dac6c856f62cd901 ]

To prevent races between smc_lgr_terminate() and smc_conn_free() add an
extra check of the lgr field before accessing it, and cancel a delayed
free_work when a new smc connection is created.
This fixes the problem that free_work cleared the lgr variable but
smc_lgr_terminate() or smc_conn_free() still access it in parallel.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index f04a037dc96774e7f2cd94fce15d373d411795f1..0de788fa43e95d7db4ae3e0bf3be9f804163552b 100644 (file)
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -103,6 +103,8 @@ static void smc_lgr_unregister_conn(struct smc_connection *conn)
        struct smc_link_group *lgr = conn->lgr;
        int reduced = 0;
 
+       if (!lgr)
+               return;
        write_lock_bh(&lgr->conns_lock);
        if (conn->alert_token_local) {
                reduced = 1;
@@ -431,6 +433,8 @@ int smc_conn_create(struct smc_sock *smc, __be32 peer_in_addr,
                        local_contact = SMC_REUSE_CONTACT;
                        conn->lgr = lgr;
                        smc_lgr_register_conn(conn); /* add smc conn to lgr */
+                       if (delayed_work_pending(&lgr->free_work))
+                               cancel_delayed_work(&lgr->free_work);
                        write_unlock_bh(&lgr->conns_lock);
                        break;
                }