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authorEric Dumazet <edumazet@google.com>2024-06-07 14:56:52 +0200
committerJakub Kicinski <kuba@kernel.org>2024-06-11 04:50:10 +0200
commit36534d3c54537bf098224a32dc31397793d4594d (patch)
tree74e1e08dbe4c54a9d2841bf054b86aa09d2010d9 /net/ipv4
parentMerge branch 'mptcp-various-fixes' (diff)
downloadlinux-36534d3c54537bf098224a32dc31397793d4594d.tar.xz
linux-36534d3c54537bf098224a32dc31397793d4594d.zip
tcp: use signed arithmetic in tcp_rtx_probe0_timed_out()
Due to timer wheel implementation, a timer will usually fire after its schedule. For instance, for HZ=1000, a timeout between 512ms and 4s has a granularity of 64ms. For this range of values, the extra delay could be up to 63ms. For TCP, this means that tp->rcv_tstamp may be after inet_csk(sk)->icsk_timeout whenever the timer interrupt finally triggers, if one packet came during the extra delay. We need to make sure tcp_rtx_probe0_timed_out() handles this case. Fixes: e89688e3e978 ("net: tcp: fix unexcepted socket die when snd_wnd is 0") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Menglong Dong <imagedong@tencent.com> Acked-by: Neal Cardwell <ncardwell@google.com> Reviewed-by: Jason Xing <kerneljasonxing@gmail.com> Link: https://lore.kernel.org/r/20240607125652.1472540-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/tcp_timer.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 83fe7f62f7f1..5bfd76a31af6 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -485,8 +485,12 @@ static bool tcp_rtx_probe0_timed_out(const struct sock *sk,
{
const struct tcp_sock *tp = tcp_sk(sk);
const int timeout = TCP_RTO_MAX * 2;
- u32 rcv_delta;
+ s32 rcv_delta;
+ /* Note: timer interrupt might have been delayed by at least one jiffy,
+ * and tp->rcv_tstamp might very well have been written recently.
+ * rcv_delta can thus be negative.
+ */
rcv_delta = inet_csk(sk)->icsk_timeout - tp->rcv_tstamp;
if (rcv_delta <= timeout)
return false;