[PATCH net 6/6] mptcp: properly account bulk freed memory
From: Mat Martineau <hidden>
Date: 2021-07-10 00:21:10
Also in:
mptcp
Subsystem:
networking [general], networking [mptcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Matthieu Baerts, Mat Martineau, Linus Torvalds
From: Paolo Abeni <pabeni@redhat.com>
After commit 879526030c8b ("mptcp: protect the rx path with
the msk socket spinlock") the rmem currently used by a given
msk is really sk_rmem_alloc - rmem_released.
The safety check in mptcp_data_ready() does not take the above
in due account, as a result legit incoming data is kept in
subflow receive queue with no reason, delaying or blocking
MPTCP-level ack generation.
This change addresses the issue introducing a new helper to fetch
the rmem memory and using it as needed. Additionally add a MIB
counter for the exceptional event described above - the peer is
misbehaving.
Finally, introduce the required annotation when rmem_released is
updated.
Fixes: 879526030c8b ("mptcp: protect the rx path with the msk socket spinlock")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/211
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <redacted>
---
net/mptcp/mib.c | 1 +
net/mptcp/mib.h | 1 +
net/mptcp/protocol.c | 12 +++++++-----
net/mptcp/protocol.h | 10 +++++++++-
4 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c
index 52ea2517e856..ff2cc0e3273d 100644
--- a/net/mptcp/mib.c
+++ b/net/mptcp/mib.c@@ -44,6 +44,7 @@ static const struct snmp_mib mptcp_snmp_list[] = { SNMP_MIB_ITEM("RmSubflow", MPTCP_MIB_RMSUBFLOW), SNMP_MIB_ITEM("MPPrioTx", MPTCP_MIB_MPPRIOTX), SNMP_MIB_ITEM("MPPrioRx", MPTCP_MIB_MPPRIORX), + SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED), SNMP_MIB_SENTINEL };
diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
index 193466c9b549..0663cb12b448 100644
--- a/net/mptcp/mib.h
+++ b/net/mptcp/mib.h@@ -37,6 +37,7 @@ enum linux_mptcp_mib_field { MPTCP_MIB_RMSUBFLOW, /* Remove a subflow */ MPTCP_MIB_MPPRIOTX, /* Transmit a MP_PRIO */ MPTCP_MIB_MPPRIORX, /* Received a MP_PRIO */ + MPTCP_MIB_RCVPRUNED, /* Incoming packet dropped due to memory limit */ __MPTCP_MIB_MAX };
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 7a5afa8c6866..a88924947815 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c@@ -474,7 +474,7 @@ static void mptcp_cleanup_rbuf(struct mptcp_sock *msk) bool cleanup, rx_empty; cleanup = (space > 0) && (space >= (old_space << 1)); - rx_empty = !atomic_read(&sk->sk_rmem_alloc); + rx_empty = !__mptcp_rmem(sk); mptcp_for_each_subflow(msk, subflow) { struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
@@ -720,8 +720,10 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk) sk_rbuf = ssk_rbuf; /* over limit? can't append more skbs to msk, Also, no need to wake-up*/ - if (atomic_read(&sk->sk_rmem_alloc) > sk_rbuf) + if (__mptcp_rmem(sk) > sk_rbuf) { + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED); return; + } /* Wake-up the reader only for in-sequence data */ mptcp_data_lock(sk);
@@ -1754,7 +1756,7 @@ static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk, if (!(flags & MSG_PEEK)) { /* we will bulk release the skb memory later */ skb->destructor = NULL; - msk->rmem_released += skb->truesize; + WRITE_ONCE(msk->rmem_released, msk->rmem_released + skb->truesize); __skb_unlink(skb, &msk->receive_queue); __kfree_skb(skb); }
@@ -1873,7 +1875,7 @@ static void __mptcp_update_rmem(struct sock *sk) atomic_sub(msk->rmem_released, &sk->sk_rmem_alloc); sk_mem_uncharge(sk, msk->rmem_released); - msk->rmem_released = 0; + WRITE_ONCE(msk->rmem_released, 0); } static void __mptcp_splice_receive_queue(struct sock *sk)
@@ -2380,7 +2382,7 @@ static int __mptcp_init_sock(struct sock *sk) msk->out_of_order_queue = RB_ROOT; msk->first_pending = NULL; msk->wmem_reserved = 0; - msk->rmem_released = 0; + WRITE_ONCE(msk->rmem_released, 0); msk->tx_pending_data = 0; msk->first = NULL;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 426ed80fe72f..0f0c026c5f8b 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h@@ -296,9 +296,17 @@ static inline struct mptcp_sock *mptcp_sk(const struct sock *sk) return (struct mptcp_sock *)sk; } +/* the msk socket don't use the backlog, also account for the bulk + * free memory + */ +static inline int __mptcp_rmem(const struct sock *sk) +{ + return atomic_read(&sk->sk_rmem_alloc) - READ_ONCE(mptcp_sk(sk)->rmem_released); +} + static inline int __mptcp_space(const struct sock *sk) { - return tcp_space(sk) + READ_ONCE(mptcp_sk(sk)->rmem_released); + return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) - __mptcp_rmem(sk)); } static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk)
--
2.32.0