From fdef3ab0211b87d886c8a87fe46be53c0642ee0c Mon Sep 17 00:00:00 2001 From: jtl Date: Fri, 6 May 2016 01:26:58 +0000 Subject: MFC r298408: Prevent underflows in tp->snd_wnd if the remote side ACKs more than tp->snd_wnd. This can happen, for example, when the remote side responds to a window probe by ACKing the one byte it contains. --- sys/netinet/tcp_input.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'sys/netinet/tcp_input.c') diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c index 32133ae..435383d 100644 --- a/sys/netinet/tcp_input.c +++ b/sys/netinet/tcp_input.c @@ -2733,6 +2733,9 @@ process_ACK: INP_WLOCK_ASSERT(tp->t_inpcb); acked = BYTES_THIS_ACK(tp, th); + KASSERT(acked >= 0, ("%s: acked unexepectedly negative " + "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, + tp->snd_una, th->th_ack, tp, m)); TCPSTAT_INC(tcps_rcvackpack); TCPSTAT_ADD(tcps_rcvackbyte, acked); @@ -2802,13 +2805,19 @@ process_ACK: SOCKBUF_LOCK(&so->so_snd); if (acked > so->so_snd.sb_cc) { - tp->snd_wnd -= so->so_snd.sb_cc; + if (tp->snd_wnd >= so->so_snd.sb_cc) + tp->snd_wnd -= so->so_snd.sb_cc; + else + tp->snd_wnd = 0; mfree = sbcut_locked(&so->so_snd, (int)so->so_snd.sb_cc); ourfinisacked = 1; } else { mfree = sbcut_locked(&so->so_snd, acked); - tp->snd_wnd -= acked; + if (tp->snd_wnd >= (u_long) acked) + tp->snd_wnd -= acked; + else + tp->snd_wnd = 0; ourfinisacked = 0; } /* NB: sowwakeup_locked() does an implicit unlock. */ -- cgit v1.1