From 057139d3830bb94df8031bb6e8e385cef53352bc Mon Sep 17 00:00:00 2001 From: David Goulet Date: Mon, 11 Dec 2017 15:42:28 -0500 Subject: sched: Avoid integer overflow when computing tcp_space In KIST, we could have a small congestion window value than the unacked packets leading to a integer overflow which leaves the tcp_space value to be humongous. This has no security implications but it results in KIST scheduler allowing to send cells on a potentially saturated connection. Found by #24423. Fixes #24590. Signed-off-by: David Goulet --- src/or/scheduler_kist.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'src') diff --git a/src/or/scheduler_kist.c b/src/or/scheduler_kist.c index 3d8f553ac2..9acd89b37f 100644 --- a/src/or/scheduler_kist.c +++ b/src/or/scheduler_kist.c @@ -264,10 +264,13 @@ update_socket_info_impl, (socket_table_ent_t *ent)) * ^ ((cwnd * mss) * factor) bytes */ - /* Assuming all these values from the kernel are uint32_t still, they will - * always fit into a int64_t tcp_space variable. */ - tcp_space = (ent->cwnd - ent->unacked) * (int64_t)ent->mss; - if (tcp_space < 0) { + /* These values from the kernel are uint32_t, they will always fit into a + * int64_t tcp_space variable but if the congestion window cwnd is smaller + * than the unacked packets, the remaining TCP space is set to 0 so we don't + * write more on this channel. */ + if (ent->cwnd >= ent->unacked) { + tcp_space = (ent->cwnd - ent->unacked) * (int64_t)(ent->mss); + } else { tcp_space = 0; } -- cgit v1.2.3-54-g00ecf