mptcp: fix recvbuffer adjust on sleeping rcvmsg

commit 449e6912a2522af672e99992e1201a454910864e upstream.

If the recvmsg() blocks after receiving some data - i.e. due to
SO_RCVLOWAT - the MPTCP code will attempt multiple times to
adjust the receive buffer size, wrongly accounting every time the
cumulative of received data - instead of accounting only for the
delta.

Address the issue moving mptcp_rcv_space_adjust just after the
data reception and passing it only the just received bytes.

This also removes an unneeded difference between the TCP and MPTCP
RX code path implementation.

Fixes: 581302298524 ("mptcp: error out earlier on disconnect")
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://patch.msgid.link/20241230-net-mptcp-rbuf-fixes-v1-1-8608af434ceb@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 370afcac2623475791dfe2c481e87455e7aa8711..57b632fb3163ae442603f85c697c9f138c54f9e7 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1917,6 +1917,8 @@ do_error:
        goto out;
 }
 
+static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied);
+
 static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
                                struct msghdr *msg,
                                size_t len, int flags,
@@ -1968,6 +1970,7 @@ static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
                        break;
        }
 
+       mptcp_rcv_space_adjust(msk, copied);
        return copied;
 }
 
@@ -2246,7 +2249,6 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
                }
 
                pr_debug("block timeout %ld\n", timeo);
-               mptcp_rcv_space_adjust(msk, copied);
                err = sk_wait_data(sk, &timeo, NULL);
                if (err < 0) {
                        err = copied ? : err;
@@ -2254,8 +2256,6 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
                }
        }
 
-       mptcp_rcv_space_adjust(msk, copied);
-
 out_err:
        if (cmsg_flags && copied >= 0) {
                if (cmsg_flags & MPTCP_CMSG_TS)