6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paolo Abeni <pabeni@xxxxxxxxxx>
commit 6bec041147a2a64a490d1f813e8a004443061b38 upstream.
In case multiple subflows race to update the mptcp-level receive
window, the subflow losing the race should use the window value
provided by the "winning" subflow to update it's own tcp-level
rcv_wnd.
To such goal, the current code bogusly uses the mptcp-level rcv_wnd
value as observed before the update attempt. On unlucky circumstances
that may lead to TCP-level window shrinkage, and stall the other end.
Address the issue feeding to the rcv wnd update the correct value.
Fixes: f3589be0c420 ("mptcp: never shrink offered window")
Cc: stable@xxxxxxxxxxxxxxx
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/427
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/mptcp/options.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -1269,12 +1269,13 @@ static void mptcp_set_rwin(struct tcp_so
if (rcv_wnd == rcv_wnd_old)
break;
- if (before64(rcv_wnd_new, rcv_wnd)) {
+
+ rcv_wnd_old = rcv_wnd;
+ if (before64(rcv_wnd_new, rcv_wnd_old)) {
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
goto raise_win;
}
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
- rcv_wnd_old = rcv_wnd;
}
return;
}
