6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paolo Abeni commit 2b0f561f21b27c40c91ea4975268a06092bd7e9c upstream. Once in a blue moon, the mptcp receive path can recursively call mptcp_data_ready() via state change under unlucky error conditions, and then try to hold the data lock again. Break the recursion loop explicitly checking for the exceptional condition. Add a new flag instead of using an existing one like 'closing', to exit early in subflow_state_change(), and explicitly flush the RX queue at reset time. This avoids unneeded processing to check for available data -- calling get_mapping_status() and more on a dying subflow -- but also in error reporting and worker scheduling. Note that we must consume the currently peeked skb before invoking mptcp_dss_corruption to avoid consuming it again after the eventual reset has freed it. Fixes: e32d262c89e2 ("mptcp: handle consistently DSS corruption") Cc: stable@vger.kernel.org Reported-by: Xinyang Ge Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-1-0cf5c72667c8@kernel.org Signed-off-by: Jakub Kicinski [ Note: conflict in protocol.c, because commit e0ca4057e0ec ("mptcp: micro-optimize __mptcp_move_skb()") is not in this version, and is part of a consequent rx path refactor. The conflict is in the context, and is easy to resolve, "done = true" can be moved along without consequences. Also a conflict in protocol.h, because __unused is at a different number. Decrement the one from this version and add the new flag above.] Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.c | 6 +++--- net/mptcp/protocol.h | 3 ++- net/mptcp/subflow.c | 11 +++++++++++ 3 files changed, 16 insertions(+), 4 deletions(-) --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -747,13 +747,13 @@ static bool __mptcp_move_skbs_from_subfl mptcp_dss_corruption(msk, ssk); } } else { + sk_eat_skb(ssk, skb); + done = true; + if (unlikely(!fin)) { DEBUG_NET_WARN_ON_ONCE(1); mptcp_dss_corruption(msk, ssk); } - - sk_eat_skb(ssk, skb); - done = true; } WRITE_ONCE(tp->copied_seq, seq); --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -510,7 +510,8 @@ struct mptcp_subflow_context { valid_csum_seen : 1, /* at least one csum validated */ is_mptfo : 1, /* subflow is doing TFO */ close_event_done : 1, /* has done the post-closed part */ - __unused : 8; + resetting : 1, /* subflow is resetting */ + __unused : 7; bool data_avail; bool scheduled; bool pm_listener; /* a listener managed by the kernel PM? */ --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -421,6 +421,10 @@ void mptcp_subflow_reset(struct sock *ss /* must hold: tcp_done() could drop last reference on parent */ sock_hold(sk); + subflow->resetting = 1; + + /* No need to delay the actual close for to-be discarded data. */ + __skb_queue_purge(&ssk->sk_receive_queue); tcp_send_active_reset(ssk, GFP_ATOMIC); tcp_done(ssk); if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags)) @@ -1802,6 +1806,13 @@ static void subflow_state_change(struct __subflow_state_change(sk); + /* Rx queue processing is unneeded, error reporting will take place at + * __mptcp_close_ssk() time and subflow reset can't happen in case of + * fallback: subflow_sched_work_if_closed() would be a no-op. + */ + if (subflow->resetting) + return; + /* as recvmsg() does not acquire the subflow socket for ssk selection * a fin packet carrying a DSS can be unnoticed if we don't trigger * the data available machinery here.