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mptcp: fix spurious wake-up on under memory pressure

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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: 5684ab1a0e ("mptcp: give rcvlowat some love")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250113-net-mptcp-connect-st-flakes-v1-2-0d986ee7b1b6@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paolo Abeni
2025-01-13 16:44:57 +01:00
committed by Greg Kroah-Hartman
parent 34e8ad3f23
commit 470f313603
1 changed files with 7 additions and 2 deletions
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net/mptcp/protocol.h
+7 -2
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@@ -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);