mptcp: fix subflow rcvbuf adjust

The mptcp PM can add subflow to the conn_list before tcp_init_transfer().
Calling tcp_rcvbuf_grow() on such subflow is not correct as later
init will overwrite the update.

Fix the issue calling tcp_rcvbuf_grow() only after init buffer
initialization.

Fixes: e118cdc34dd1 ("mptcp: rcvbuf auto-tuning improvement")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251028-net-tcp-recv-autotune-v3-1-74b43ba4c84c@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 0292162a14eedffde166cc2a2d4eaa7c3aa6760d..a8a3bdf955437e90ff58624cff4e4b9d54daf015 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2051,6 +2051,7 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied)
 
        msk->rcvq_space.space = msk->rcvq_space.copied;
        if (mptcp_rcvbuf_grow(sk)) {
+               int copied = msk->rcvq_space.copied;
 
                /* Make subflows follow along.  If we do not do this, we
                 * get drops at subflow level if skbs can't be moved to
@@ -2063,8 +2064,11 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied)
 
                        ssk = mptcp_subflow_tcp_sock(subflow);
                        slow = lock_sock_fast(ssk);
-                       tcp_sk(ssk)->rcvq_space.space = msk->rcvq_space.copied;
-                       tcp_rcvbuf_grow(ssk);
+                       /* subflows can be added before tcp_init_transfer() */
+                       if (tcp_sk(ssk)->rcvq_space.space) {
+                               tcp_sk(ssk)->rcvq_space.space = copied;
+                               tcp_rcvbuf_grow(ssk);
+                       }
                        unlock_sock_fast(ssk, slow);
                }
        }