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Message-ID: <20250828195823.3958522-8-edumazet@google.com>
Date: Thu, 28 Aug 2025 19:58:22 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Neal Cardwell <ncardwell@...gle.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>,
David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 7/8] tcp: use dst_dev_rcu() in tcp_fastopen_active_disable_ofo_check()
Use RCU to avoid a pair of atomic operations and a potential
UAF on dst_dev()->flags.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/ipv4/tcp_fastopen.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index f1884f0c9e523d50b2d120175cc94bc40b489dfb..7d945a527daf093f87882c7949e21058ed6df1cc 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -576,11 +576,12 @@ void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
}
} else if (tp->syn_fastopen_ch &&
atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times)) {
- dst = sk_dst_get(sk);
- dev = dst ? dst_dev(dst) : NULL;
+ rcu_read_lock();
+ dst = __sk_dst_get(sk);
+ dev = dst ? dst_dev_rcu(dst) : NULL;
if (!(dev && (dev->flags & IFF_LOOPBACK)))
atomic_set(&sock_net(sk)->ipv4.tfo_active_disable_times, 0);
- dst_release(dst);
+ rcu_read_unlock();
}
}
--
2.51.0.318.gd7df087d1a-goog
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