[PATCH net 3/9] net/smc: prevent races between smc_lgr_terminate() and smc_conn_free()

[Ursula Braun]

From: Karsten Graul <kgr...@linux.ibm.com>

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 <kgr...@linux.ibm.com>
Signed-off-by: Ursula Braun <ubr...@linux.ibm.com>
---
 net/smc/smc_core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 35c1cdc93e1c..097c798983ca 100644
--- 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;
                }
-- 
2.16.4