mptcp: avoid data corruption on reinsert

When updating a partially acked data fragment, we actually corrupt it. This is irrelevant till we send data on a single subflow, as retransmitted data, if any are discarded by the peer as duplicate, but it will cause data corruption as soon as we will start creating non backup subflows. Reviewed-by: Mat Martineau <[email protected]> Tested-by: Christoph Paasch <[email protected]> Signed-off-by: Paolo Abeni <[email protected]> Signed-off-by: David S. Miller <[email protected]>
chewitt · Jul 23, 2020 · 53eb4c3 · 53eb4c3
1 parent b0977bb
commit 53eb4c3
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
@@ -460,15 +460,20 @@ static void mptcp_clean_una(struct sock *sk)
 
 	dfrag = mptcp_rtx_head(sk);
 	if (dfrag && after64(snd_una, dfrag->data_seq)) {
-		u64 delta = dfrag->data_seq + dfrag->data_len - snd_una;
+		u64 delta = snd_una - dfrag->data_seq;
+
+		if (WARN_ON_ONCE(delta > dfrag->data_len))
+			goto out;
 
 		dfrag->data_seq += delta;
+		dfrag->offset += delta;
 		dfrag->data_len -= delta;
 
 		dfrag_uncharge(sk, delta);
 		cleaned = true;
 	}
 
+out:
 	if (cleaned) {
 		sk_mem_reclaim_partial(sk);