6.1-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Abeni pabeni@redhat.com
commit 68cc924729ffcfe90d0383177192030a9aeb2ee4 upstream.
When a subflow receives and discards duplicate data, the mptcp stack assumes that the consumed offset inside the current skb is zero.
With multiple subflows receiving data simultaneously such assertion does not held true. As a result the subflow-level copied_seq will be incorrectly increased and later on the same subflow will observe a bad mapping, leading to subflow reset.
Address the issue taking into account the skb consumed offset in mptcp_subflow_discard_data().
Fixes: 04e4cd4f7ca4 ("mptcp: cleanup mptcp_subflow_discard_data()") Cc: stable@vger.kernel.org Link: https://github.com/multipath-tcp/mptcp_net-next/issues/501 Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/subflow.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
--- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1103,14 +1103,22 @@ static void mptcp_subflow_discard_data(s { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); bool fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN; - u32 incr; + struct tcp_sock *tp = tcp_sk(ssk); + u32 offset, incr, avail_len;
- incr = limit >= skb->len ? skb->len + fin : limit; + offset = tp->copied_seq - TCP_SKB_CB(skb)->seq; + if (WARN_ON_ONCE(offset > skb->len)) + goto out;
- pr_debug("discarding=%d len=%d seq=%d", incr, skb->len, - subflow->map_subflow_seq); + avail_len = skb->len - offset; + incr = limit >= avail_len ? avail_len + fin : limit; + + pr_debug("discarding=%d len=%d offset=%d seq=%d", incr, skb->len, + offset, subflow->map_subflow_seq); MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DUPDATA); tcp_sk(ssk)->copied_seq += incr; + +out: if (!before(tcp_sk(ssk)->copied_seq, TCP_SKB_CB(skb)->end_seq)) sk_eat_skb(ssk, skb); if (mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len)