5.15-stable review patch. If anyone has any objections, please let me know.
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From: Matthieu Baerts (NGI0) matttbe@kernel.org
commit 21c02e8272bc95ba0dd44943665c669029b42760 upstream.
Recently, during a debugging session using local MPTCP connections, I noticed MPJoinAckHMacFailure was not zero on the server side. The counter was in fact incremented when the PM rejected new subflows, because the 'subflow' limit was reached.
The fix is easy, simply dissociating the two cases: only the HMAC validation check should increase MPTCP_MIB_JOINACKMAC counter.
Fixes: 4cf8b7e48a09 ("subflow: introduce and use mptcp_can_accept_new_subflow()") Cc: stable@vger.kernel.org Reviewed-by: Geliang Tang geliang@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/20250407-net-mptcp-hmac-failure-mib-v1-1-3c9ecd0a3a... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/subflow.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -782,12 +782,16 @@ create_child: goto dispose_child; }
- if (!subflow_hmac_valid(req, &mp_opt) || - !mptcp_can_accept_new_subflow(subflow_req->msk)) { + if (!subflow_hmac_valid(req, &mp_opt)) { SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC); subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT); goto dispose_child; } + + if (!mptcp_can_accept_new_subflow(owner)) { + subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT); + goto dispose_child; + }
/* move the msk reference ownership to the subflow */ subflow_req->msk = NULL;