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

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>

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 35c1cdc93e1c54c3ad0003aea46f0b7597a7e872..097c798983ca91ab5e071dbe175529af657a77a4 100644 (file)
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -128,6 +128,8 @@ static void smc_lgr_unregister_conn(struct smc_connection *conn)
 {
        struct smc_link_group *lgr = conn->lgr;
 
+       if (!lgr)
+               return;
        write_lock_bh(&lgr->conns_lock);
        if (conn->alert_token_local) {
                __smc_lgr_unregister_conn(conn);
@@ -628,6 +630,8 @@ int smc_conn_create(struct smc_sock *smc, bool is_smcd, int srv_first_contact,
                        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;
                }