netdev - [PATCH v2 net 16/17] net: Fix a data-race around netdev_unregister_timeout

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Date:   Wed, 17 Aug 2022 20:52:26 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
CC:     Kuniyuki Iwashima <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>, Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH v2 net 16/17] 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: 5aa3afe107d9 ("net: make unregister netdev warning timeout configurable")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
CC: Dmitry Vyukov <dvyukov@...gle.com>
---
 net/core/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 8221322d86db..56c8b0921c9f 100644
--- 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));
-- 
2.30.2