From: Paolo Abeni <pabeni@xxxxxxxxxx> commit 29249eac5225429b898f278230a6ca2baa1ae154 upstream. Maxim reported several issues when forcing a TCP transparent proxy to use the MPTCP protocol for the inbound connections. He also provided a clean reproducer. The problem boils down to 'mptcp_frag_can_collapse_to()' assuming that only MPTCP will use the given page_frag. If others - e.g. the plain TCP protocol - allocate page fragments, we can end-up re-using already allocated memory for mptcp_data_frag. Fix the issue ensuring that the to-be-expanded data fragment is located at the current page frag end. v1 -> v2: - added missing fixes tag (Mat) Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/178 Reported-and-tested-by: Maxim Galaganov <max@xxxxxxxxxxx> Fixes: 18b683bff89d ("mptcp: queue data for mptcp level retransmission") Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/mptcp/protocol.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -869,12 +869,18 @@ static bool mptcp_skb_can_collapse_to(u6 !mpext->frozen; } +/* we can append data to the given data frag if: + * - there is space available in the backing page_frag + * - the data frag tail matches the current page_frag free offset + * - the data frag end sequence number matches the current write seq + */ static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk, const struct page_frag *pfrag, const struct mptcp_data_frag *df) { return df && pfrag->page == df->page && pfrag->size - pfrag->offset > 0 && + pfrag->offset == (df->offset + df->data_len) && df->data_seq + df->data_len == msk->write_seq; }
