commit d0b24860363a3704e28569ce9a6987717834edea

Author: Miroslav Lichvar <mlichvar@redhat.com>

Date:   Tue Dec 5 11:08:24 2017 +0100

    client: don't call select() with invalid timeout

    If the system clock was stepped forward after chronyc sent a request and

    before it read the clock in order to calculate the receive timeout,

    select() could be called with a negative timeout, which resulted in an

    infinite loop waiting for select() to succeed.

    Fix the submit_request() function to not call select() with a negative

    timeout. Also, return immediately on any error of select().

diff --git a/client.c b/client.c

index 5c3a99e..4e23158 100644

--- a/client.c

+++ b/client.c

@@ -1394,9 +1394,16 @@ submit_request(CMD_Request *request, CMD_Reply *reply)

     timeout = initial_timeout / 1000.0 * (1U << (n_attempts - 1)) -

               UTI_DiffTimespecsToDouble(&ts_now, &ts_start);

-    UTI_DoubleToTimeval(timeout, &tv;;

     DEBUG_LOG("Timeout %f seconds", timeout);

+    /* Avoid calling select() with an invalid timeout */

+    if (timeout <= 0.0) {

+      new_attempt = 1;

+      continue;

+    }

+

+    UTI_DoubleToTimeval(timeout, &tv;;

+

     FD_ZERO(&rdfd);

     FD_ZERO(&wrfd);

     FD_ZERO(&exfd);

@@ -1410,6 +1417,7 @@ submit_request(CMD_Request *request, CMD_Reply *reply)

     if (select_status < 0) {

       DEBUG_LOG("select failed : %s", strerror(errno));

+      return 0;

     } else if (select_status == 0) {

       /* Timeout must have elapsed, try a resend? */

       new_attempt = 1;