From 470f313603df0c2e77ea55cbccb61de5b67f3a91 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Mon, 13 Jan 2025 16:44:57 +0100 Subject: [PATCH] mptcp: fix spurious wake-up on under memory pressure commit e226d9259dc4f5d2c19e6682ad1356fa97cf38f4 upstream. The wake-up condition currently implemented by mptcp_epollin_ready() is wrong, as it could mark the MPTCP socket as readable even when no data are present and the system is under memory pressure. Explicitly check for some data being available in the receive queue. Fixes: 5684ab1a0eff ("mptcp: give rcvlowat some love") Cc: stable@vger.kernel.org Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250113-net-mptcp-connect-st-flakes-v1-2-0d986ee7b1b6@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index a93e661ef5c4..73526f1d768f 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -760,10 +760,15 @@ static inline u64 mptcp_data_avail(const struct mptcp_sock *msk) static inline bool mptcp_epollin_ready(const struct sock *sk) { + u64 data_avail = mptcp_data_avail(mptcp_sk(sk)); + + if (!data_avail) + return false; + /* mptcp doesn't have to deal with small skbs in the receive queue, - * at it can always coalesce them + * as it can always coalesce them */ - return (mptcp_data_avail(mptcp_sk(sk)) >= sk->sk_rcvlowat) || + return (data_avail >= sk->sk_rcvlowat) || (mem_cgroup_sockets_enabled && sk->sk_memcg && mem_cgroup_under_socket_pressure(sk->sk_memcg)) || READ_ONCE(tcp_memory_pressure);