From e02d90e0ab2b858bd85be193e6e5c545f6cab8ab Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Wed, 31 Jul 2024 12:10:15 +0200 Subject: [PATCH] mptcp: fix duplicate data handling 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 Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman --- net/mptcp/subflow.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 276fe9f44df73..823a92b21c6cf 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -863,14 +863,22 @@ static void mptcp_subflow_discard_data(struct sock *ssk, struct sk_buff *skb, { 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; + + avail_len = skb->len - offset; + incr = limit >= avail_len ? avail_len + fin : limit; - pr_debug("discarding=%d len=%d seq=%d", incr, skb->len, - subflow->map_subflow_seq); + 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)