| From | Andi Kleen <> | Subject | [PATCH] [49/139] tcp: avoid a possible divide by zero | Date | Tue, 1 Feb 2011 16:44:05 -0800 (PST) |
| |
2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <eric.dumazet@gmail.com>
[ Upstream commit ad9f4f50fe9288bbe65b7dfd76d8820afac6a24c ]
sysctl_tcp_tso_win_divisor might be set to zero while one cpu runs in tcp_tso_should_defer(). Make sure we dont allow a divide by zero by reading sysctl_tcp_tso_win_divisor exactly once.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Andi Kleen <ak@linux.intel.com>
--- net/ipv4/tcp_output.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
Index: linux-2.6.35.y/net/ipv4/tcp_output.c =================================================================== --- linux-2.6.35.y.orig/net/ipv4/tcp_output.c +++ linux-2.6.35.y/net/ipv4/tcp_output.c @@ -1516,6 +1516,7 @@ static int tcp_tso_should_defer(struct s struct tcp_sock *tp = tcp_sk(sk); const struct inet_connection_sock *icsk = inet_csk(sk); u32 send_win, cong_win, limit, in_flight; + int win_divisor; if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) goto send_now; @@ -1547,13 +1548,14 @@ static int tcp_tso_should_defer(struct s if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len)) goto send_now; - if (sysctl_tcp_tso_win_divisor) { + win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor); + if (win_divisor) { u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); /* If at least some fraction of a window is available, * just use it. */ - chunk /= sysctl_tcp_tso_win_divisor; + chunk /= win_divisor; if (limit >= chunk) goto send_now; } else {
|