net/smc: Reset conn->lgr when link group registration fails

SMC connections might fail to be registered in a link group due to
unable to find a usable link during its creation. As a result,
smc_conn_create() will return a failure and most resources related
to the connection won't be applied or initialized, such as
conn->abort_work or conn->lnk.

If smc_conn_free() is invoked later, it will try to access the
uninitialized resources related to the connection, thus causing
a warning or crash.

This patch tries to fix this by resetting conn->lgr to NULL if an
abnormal exit occurs in smc_lgr_register_conn(), thus avoiding the
access to uninitialized resources in smc_conn_free().

Meanwhile, the new created link group should be terminated if smc
connections can't be registered in it. So smc_lgr_cleanup_early() is
modified to take care of link group only and invoked to terminate
unusable link group by smc_conn_create(). The call to smc_conn_free()
is moved out from smc_lgr_cleanup_early() to smc_conn_abort().

Fixes: 56bc3b2094b4 ("net/smc: assign link to a new connection")
Suggested-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Acked-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index a6849362f4dd..c9a8092c4ac9 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -171,8 +171,10 @@ static int smc_lgr_register_conn(struct smc_connection *conn, bool first)
 
 	if (!conn->lgr->is_smcd) {
 		rc = smcr_lgr_conn_assign_link(conn, first);
-		if (rc)
+		if (rc) {
+			conn->lgr = NULL;
 			return rc;
+		}
 	}
 	/* find a new alert_token_local value not yet used by some connection
 	 * in this link group
@@ -622,15 +624,13 @@ int smcd_nl_get_lgr(struct sk_buff *skb, struct netlink_callback *cb)
 	return skb->len;
 }
 
-void smc_lgr_cleanup_early(struct smc_connection *conn)
+void smc_lgr_cleanup_early(struct smc_link_group *lgr)
 {
-	struct smc_link_group *lgr = conn->lgr;
 	spinlock_t *lgr_lock;
 
 	if (!lgr)
 		return;
 
-	smc_conn_free(conn);
 	smc_lgr_list_head(lgr, &lgr_lock);
 	spin_lock_bh(lgr_lock);
 	/* do not use this link group for new connections */
@@ -1832,8 +1832,10 @@ create:
 		write_lock_bh(&lgr->conns_lock);
 		rc = smc_lgr_register_conn(conn, true);
 		write_unlock_bh(&lgr->conns_lock);
-		if (rc)
+		if (rc) {
+			smc_lgr_cleanup_early(lgr);
 			goto out;
+		}
 	}
 	conn->local_tx_ctrl.common.type = SMC_CDC_MSG_TYPE;
 	conn->local_tx_ctrl.len = SMC_WR_TX_SIZE;