[PATCH 5.4 30/71] ipv4: Fix a data-race around sysctl_fib_sync_mem.

[Greg Kroah-Hartman]

From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>

[ Upstream commit 73318c4b7dbd0e781aaababff17376b2894745c0 ]

While reading sysctl_fib_sync_mem, it can be changed concurrently.
So, we need to add READ_ONCE() to avoid a data-race.

Fixes: 9ab948a91b2c ("ipv4: Allow amount of dirty memory from fib resizing to be controllable")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ipv4/fib_trie.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 51673d00bbea..a1f830da4ad3 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -500,7 +500,7 @@ static void tnode_free(struct key_vector *tn)
 		tn = container_of(head, struct tnode, rcu)->kv;
 	}
 
-	if (tnode_free_size >= sysctl_fib_sync_mem) {
+	if (tnode_free_size >= READ_ONCE(sysctl_fib_sync_mem)) {
 		tnode_free_size = 0;
 		synchronize_rcu();
 	}
-- 
2.35.1