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/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;
}
}