From: Paolo Abeni pabeni@redhat.com
The MPTCP protocol can acquire the subflow-level socket lock and cause the tcp backlog usage. When inserting new skbs into the backlog, the stack will try to coalesce them.
Currently, we have no check in place to ensure that such coalescing will respect the MPTCP-level DSS, and that may cause data stream corruption, as reported by Christoph.
Address the issue by adding the relevant admission check for coalescing in tcp_add_backlog().
Note the issue is not easy to reproduce, as the MPTCP protocol tries hard to avoid acquiring the subflow-level socket lock.
Fixes: 648ef4b88673 ("mptcp: Implement MPTCP receive path") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch cpaasch@apple.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/420 Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Mat Martineau martineau@kernel.org --- net/ipv4/tcp_ipv4.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 27140e5cdc06..4167e8a48b60 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1869,6 +1869,7 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb, #ifdef CONFIG_TLS_DEVICE tail->decrypted != skb->decrypted || #endif + !mptcp_skb_can_collapse(tail, skb) || thtail->doff != th->doff || memcmp(thtail + 1, th + 1, hdrlen - sizeof(*th))) goto no_coalesce;