1 files changed, 15 insertions, 14 deletions

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index a05270996613..b5850afea343 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -942,19 +942,20 @@ reset:
 	return false;
 }
 
-static u64 expand_ack(u64 old_ack, u64 cur_ack, bool use_64bit)
+u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
 {
-	u32 old_ack32, cur_ack32;
-
-	if (use_64bit)
-		return cur_ack;
-
-	old_ack32 = (u32)old_ack;
-	cur_ack32 = (u32)cur_ack;
-	cur_ack = (old_ack & GENMASK_ULL(63, 32)) + cur_ack32;
-	if (unlikely(before(cur_ack32, old_ack32)))
-		return cur_ack + (1LL << 32);
-	return cur_ack;
+	u32 old_seq32, cur_seq32;
+
+	old_seq32 = (u32)old_seq;
+	cur_seq32 = (u32)cur_seq;
+	cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
+	if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
+		return cur_seq + (1LL << 32);
+
+	/* reverse wrap could happen, too */
+	if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
+		return cur_seq - (1LL << 32);
+	return cur_seq;
 }
 
 static void ack_update_msk(struct mptcp_sock *msk,
@@ -972,7 +973,7 @@ static void ack_update_msk(struct mptcp_sock *msk,
 	 * more dangerous than missing an ack
 	 */
 	old_snd_una = msk->snd_una;
-	new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
+	new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 
 	/* ACK for data not even sent yet? Ignore. */
 	if (after64(new_snd_una, snd_nxt))
@@ -1009,7 +1010,7 @@ bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool us
 		return false;
 
 	WRITE_ONCE(msk->rcv_data_fin_seq,
-		   expand_ack(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
+		   mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
 	WRITE_ONCE(msk->rcv_data_fin, 1);
 
 	return true;