[PATCH net-next 7/8] tcp: use dst_dev_rcu() in tcp_fastopen_active_disable_ofo_check()
From: Eric Dumazet <edumazet@google.com>
Date: 2025-08-28 19:58:47
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
Use RCU to avoid a pair of atomic operations and a potential UAF on dst_dev()->flags. Signed-off-by: Eric Dumazet <edumazet@google.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