1 files changed, 4 insertions, 2 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index ef1d02cd3a72..bc28ab1be572 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -2143,15 +2143,17 @@ process_ACK:
 				incr = incr * incr / cw;
 			tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
 		}
+		SOCKBUF_LOCK(&so->so_snd);
 		if (acked > so->so_snd.sb_cc) {
 			tp->snd_wnd -= so->so_snd.sb_cc;
-			sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
+			sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc);
 			ourfinisacked = 1;
 		} else {
-			sbdrop(&so->so_snd, acked);
+			sbdrop_locked(&so->so_snd, acked);
 			tp->snd_wnd -= acked;
 			ourfinisacked = 0;
 		}
+		SOCKBUF_UNLOCK(&so->so_snd);
 		sowwakeup(so);
 		/* detect una wraparound */
 		if ((tcp_do_newreno || tp->sack_enable) &&