From: Paolo Abeni pabeni@redhat.com

commit ce7356ae35943cc6494cc692e62d51a734062b7d upstream.

Additional active subflows - i.e. created by the in kernel path manager - are included into the subflow list before starting the 3whs.

A racing recvmsg() spooling data received on an already established subflow would unconditionally call tcp_cleanup_rbuf() on all the current subflows, potentially hitting a divide by zero error on the newly created ones.

Explicitly check that the subflow is in a suitable state before invoking tcp_cleanup_rbuf().

Fixes: c76c6956566f ("mptcp: call tcp_cleanup_rbuf on subflows") Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Matthieu Baerts (NGI0) matttbe@kernel.org Link: https://patch.msgid.link/02374660836e1b52afc91966b7535c8c5f7bafb0.1731060874... Signed-off-by: Jakub Kicinski kuba@kernel.org [ Conflicts in protocol.c, because commit f410cbea9f3d ("tcp: annotate data-races around tp->window_clamp") has not been backported to this version. The conflict is easy to resolve, because only the context is different, but not the line to modify. ] Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/protocol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 34c98596350e..bcbb1f92ce24 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1986,7 +1986,8 @@ static void mptcp_rcv_space_adjust(struct mptcp_sock *msk, int copied) slow = lock_sock_fast(ssk); WRITE_ONCE(ssk->sk_rcvbuf, rcvbuf); tcp_sk(ssk)->window_clamp = window_clamp; - tcp_cleanup_rbuf(ssk, 1); + if (tcp_can_send_ack(ssk)) + tcp_cleanup_rbuf(ssk, 1); unlock_sock_fast(ssk, slow); } }