RDS: have sockets get transport module references
Right now there's nothing to stop the various paths that use
rs->rs_transport from racing with rmmod and executing freed transport
code. The simple fix is to have binding to a transport also hold a
reference to the transport's module, removing this class of races.
We already had an unused t_owner field which was set for the modular
transports and which wasn't set for the built-in loop transport.
Signed-off-by: Zach Brown <zach.brown@oracle.com>
diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
index 57ef0ec..8e3886d 100644
--- a/net/rds/af_rds.c
+++ b/net/rds/af_rds.c
@@ -90,6 +90,8 @@
rds_sock_count--;
spin_unlock_irqrestore(&rds_sock_lock, flags);
+ rds_trans_put(rs->rs_transport);
+
sock->sk = NULL;
sock_put(sk);
out:
diff --git a/net/rds/connection.c b/net/rds/connection.c
index 75a1a37..968b7a7 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -117,6 +117,7 @@
{
struct rds_connection *conn, *parent = NULL;
struct hlist_head *head = rds_conn_bucket(laddr, faddr);
+ struct rds_transport *loop_trans;
unsigned long flags;
int ret;
@@ -163,7 +164,9 @@
* can bind to the destination address then we'd rather the messages
* flow through loopback rather than either transport.
*/
- if (rds_trans_get_preferred(faddr)) {
+ loop_trans = rds_trans_get_preferred(faddr);
+ if (loop_trans) {
+ rds_trans_put(loop_trans);
conn->c_loopback = 1;
if (is_outgoing && trans->t_prefer_loopback) {
/* "outgoing" connection - and the transport
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 2ff7fc9..aab5e94 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -798,6 +798,7 @@
int rds_trans_register(struct rds_transport *trans);
void rds_trans_unregister(struct rds_transport *trans);
struct rds_transport *rds_trans_get_preferred(__be32 addr);
+void rds_trans_put(struct rds_transport *trans);
unsigned int rds_trans_stats_info_copy(struct rds_info_iterator *iter,
unsigned int avail);
int rds_trans_init(void);
diff --git a/net/rds/transport.c b/net/rds/transport.c
index 7e10679..7f2ac4f 100644
--- a/net/rds/transport.c
+++ b/net/rds/transport.c
@@ -71,19 +71,28 @@
}
EXPORT_SYMBOL_GPL(rds_trans_unregister);
+void rds_trans_put(struct rds_transport *trans)
+{
+ if (trans && trans->t_owner)
+ module_put(trans->t_owner);
+}
+
struct rds_transport *rds_trans_get_preferred(__be32 addr)
{
struct rds_transport *ret = NULL;
- int i;
+ struct rds_transport *trans;
+ unsigned int i;
if (IN_LOOPBACK(ntohl(addr)))
return &rds_loop_transport;
down_read(&rds_trans_sem);
- for (i = 0; i < RDS_TRANS_COUNT; i++)
- {
- if (transports[i] && (transports[i]->laddr_check(addr) == 0)) {
- ret = transports[i];
+ for (i = 0; i < RDS_TRANS_COUNT; i++) {
+ trans = transports[i];
+
+ if (trans && (trans->laddr_check(addr) == 0) &&
+ (!trans->t_owner || try_module_get(trans->t_owner))) {
+ ret = trans;
break;
}
}