Commit 29249eac authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

mptcp: fix data stream corruption 

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: default avatarMaxim Galaganov <max@internet.ru>
Fixes: 18b683bf ("mptcp: queue data for mptcp level retransmission")
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent df6f8237

net/mptcp/protocol.c

+6 −0
Original line number Diff line number Diff line
@@ -879,12 +879,18 @@ static bool mptcp_skb_can_collapse_to(u64 write_seq, 
	       !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;

}