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From:   Kuniyuki Iwashima <kuniyu@amazon.com>
To:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>
CC:     Kuniyuki Iwashima <kuniyu@amazon.com>,
        Kuniyuki Iwashima <kuni1840@gmail.com>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: [PATCH v2 net 08/12] inetpeer: Fix data-races around sysctl.
Date:   Wed, 6 Jul 2022 16:39:59 -0700
Message-ID: <20220706234003.66760-9-kuniyu@amazon.com>
In-Reply-To: <20220706234003.66760-1-kuniyu@amazon.com>
References: <20220706234003.66760-1-kuniyu@amazon.com>
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While reading inetpeer sysctl variables, they can be changed
concurrently.  So, we need to add READ_ONCE() to avoid data-races.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv4/inetpeer.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index da21dfce24d7..e9fed83e9b3c 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -141,16 +141,20 @@ static void inet_peer_gc(struct inet_peer_base *base,
 			 struct inet_peer *gc_stack[],
 			 unsigned int gc_cnt)
 {
+	int peer_threshold, peer_maxttl, peer_minttl;
 	struct inet_peer *p;
 	__u32 delta, ttl;
 	int i;
 
-	if (base->total >= inet_peer_threshold)
+	peer_threshold = READ_ONCE(inet_peer_threshold);
+	peer_maxttl = READ_ONCE(inet_peer_maxttl);
+	peer_minttl = READ_ONCE(inet_peer_minttl);
+
+	if (base->total >= peer_threshold)
 		ttl = 0; /* be aggressive */
 	else
-		ttl = inet_peer_maxttl
-				- (inet_peer_maxttl - inet_peer_minttl) / HZ *
-					base->total / inet_peer_threshold * HZ;
+		ttl = peer_maxttl - (peer_maxttl - peer_minttl) / HZ *
+			base->total / peer_threshold * HZ;
 	for (i = 0; i < gc_cnt; i++) {
 		p = gc_stack[i];
 
-- 
2.30.2