[PATCH 6.7 127/162] mptcp: fix potential wake-up event loss

Greg Kroah-Hartman
2024-03-04T21:31:23Z

From: Paolo Abeni <pabeni@redhat.com>

commit b111d8fbd2cbc63e05f3adfbbe0d4df655dfcc5b upstream.

After the blamed commit below, the send buffer auto-tuning can
happen after that the mptcp_propagate_sndbuf() completes - via
the delegated action infrastructure.

We must check for write space even after such change or we risk
missing the wake-up event.

Fixes: 8005184fd1ca ("mptcp: refactor sndbuf auto-tuning")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240223-upstream-net-20240223-misc-fixes-v1-6-162e87e48497@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mptcp/protocol.h | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -790,6 +790,16 @@ static inline bool mptcp_data_fin_enable
READ_ONCE(msk->write_seq) == READ_ONCE(msk->snd_nxt);
}

+static inline void mptcp_write_space(struct sock *sk)
+{
+ if (sk_stream_is_writeable(sk)) {
+ /* pairs with memory barrier in mptcp_poll */
+ smp_mb();
+ if (test_and_clear_bit(MPTCP_NOSPACE, &mptcp_sk(sk)->flags))
+ sk_stream_write_space(sk);
+ }
+}
+
static inline void __mptcp_sync_sndbuf(struct sock *sk)
{
struct mptcp_subflow_context *subflow;
@@ -808,6 +818,7 @@ static inline void __mptcp_sync_sndbuf(s

/* the msk max wmem limit is <nr_subflows> * tcp wmem[2] */
WRITE_ONCE(sk->sk_sndbuf, new_sndbuf);
+ mptcp_write_space(sk);
}

/* The called held both the msk socket and the subflow socket locks,
@@ -838,16 +849,6 @@ static inline void mptcp_propagate_sndbu
local_bh_enable();
}

-static inline void mptcp_write_space(struct sock *sk)
-{
- if (sk_stream_is_writeable(sk)) {
- /* pairs with memory barrier in mptcp_poll */
- smp_mb();
- if (test_and_clear_bit(MPTCP_NOSPACE, &mptcp_sk(sk)->flags))
- sk_stream_write_space(sk);
- }
-}
-
void mptcp_destroy_common(struct mptcp_sock *msk, unsigned int flags);

#define MPTCP_TOKEN_MAX_RETRIES 4