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[net,2/5] tcp: check mptcp-level constraints for backlog coalescing

Message ID 20231018-send-net-20231018-v1-2-17ecb002e41d@kernel.org (mailing list archive)
State Mainlined, archived
Delegated to: Mat Martineau
Headers show
Series mptcp: Fixes for v6.6 | expand

Commit Message

Mat Martineau Oct. 18, 2023, 6:23 p.m. UTC 
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 mbox series

Patch

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;