net: Add module reference to FIB notifiers

When a listener registers to the FIB notification chain it receives a
dump of the FIB entries and rules from existing address families by
invoking their dump operations.

While we call into these modules we need to make sure they aren't
removed. Do that by increasing their reference count before invoking
their dump operations and decrease it afterwards.

Fixes: 04b1d4e50e82 ("net: core: Make the FIB notification chain generic")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 2 deletions

diff --git a/net/core/fib_notifier.c b/net/core/fib_notifier.c
index 292aab83702f..4fc202dbdfb6 100644
--- a/net/core/fib_notifier.c
+++ b/net/core/fib_notifier.c
@@ -2,6 +2,7 @@
 #include <linux/notifier.h>
 #include <linux/rcupdate.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/init.h>
 #include <net/net_namespace.h>
 #include <net/fib_notifier.h>
@@ -33,8 +34,12 @@ static unsigned int fib_seq_sum(void)
 
 	rtnl_lock();
 	for_each_net(net) {
-		list_for_each_entry(ops, &net->fib_notifier_ops, list)
+		list_for_each_entry(ops, &net->fib_notifier_ops, list) {
+			if (!try_module_get(ops->owner))
+				continue;
 			fib_seq += ops->fib_seq_read(net);
+			module_put(ops->owner);
+		}
 	}
 	rtnl_unlock();
 
@@ -46,8 +51,12 @@ static int fib_net_dump(struct net *net, struct notifier_block *nb)
 	struct fib_notifier_ops *ops;
 
 	list_for_each_entry_rcu(ops, &net->fib_notifier_ops, list) {
-		int err = ops->fib_dump(net, nb);
+		int err;
 
+		if (!try_module_get(ops->owner))
+			continue;
+		err = ops->fib_dump(net, nb);
+		module_put(ops->owner);
 		if (err)
 			return err;
 	}