net: Fix a data-race around netdev_unregister_timeout_secs.

While reading netdev_unregister_timeout_secs, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its reader.

Fixes: 2f76cf6ad290 ("net: make unregister netdev warning timeout configurable")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 8221322d86db9c012d40d2c83e58c2dd51db334d..56c8b0921c9fdc9edfd4003f019693656813c1fa 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10284,7 +10284,7 @@ static struct net_device *netdev_wait_allrefs_any(struct list_head *list)
                                return dev;
 
                if (time_after(jiffies, warning_time +
-                              netdev_unregister_timeout_secs * HZ)) {
+                              READ_ONCE(netdev_unregister_timeout_secs) * HZ)) {
                        list_for_each_entry(dev, list, todo_list) {
                                pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
                                         dev->name, netdev_refcnt_read(dev));