[Nagiosplug-devel] Flight 1.4.8, ready for boarding

Holger Weiss holger at CIS.FU-Berlin.DE
Sat Mar 31 20:53:29 CEST 2007

* Thomas Guyot-Sionnest <Thomas at zango.com> [2007-03-30 09:16]:
> There's the two bugs with check_ntp. The segfault is caused by the fact that
> the check program don't get the jitter and so it tests a pointer that
> doesn't exist. I make a patch that fixes the segfault (Uploaded in the bug
> tracker)

Your patch should be committed in any case.

> but instead it returns a warning that it can't parse the jitter or something
> like that.

What is the exact message you get?  The message "warning: unable to read
server jitter response" indicates that the server simply doesn't support
jitter control packets.  However, with all servers I tried, the plugin
returns a WARNING state _without_ explaining the problem:

| $ ./check_ntp -H time.fu-berlin.de -j 2 -k 3
| NTP WARNING: Offset 0.05885159969 secs|offset=0.05885159969 jitter=0.001171

This WARNING is issued in jitter_request():

| if(! syncsource_found) *status = STATE_WARNING;

I'm not familiar with NTP and haven't tracked down whether the plugin
does something wrong while checking for the synchronization source; and
if not, whether it should really return a WARNING state here.  If so,
the reason for the WARNING should certainly be mentioned in the plugin
output.  For the moment, I committed patch which at least adds a line
explaining the WARNING to the verbose output.

> The other is a realloc error caught by glibc on my Ubuntu box. I have no
> idea what's wrong there (It's beyond my skills)...

The memcpy(3) following the realloc(3) call writes out of bounds as soon
as peer_offset is >0.  I committed the following patch:

---------- 8< ----------------------------------------------------------
--- check_ntp.c 31 Mar 2007 17:35:08 -0000      1.17
+++ check_ntp.c 31 Mar 2007 18:40:46 -0000
@@ -506,6 +506,7 @@
        ntp_control_message req;
        double rval = 0.0, jitter = -1.0;
        char *startofvalue=NULL, *nptr=NULL;
+       void *tmp;

        /* Long-winded explanation:
         * Getting the jitter requires a number of steps:
@@ -539,8 +540,10 @@
                 * we represent as a ntp_assoc_status_pair datatype.
-               peers=(ntp_assoc_status_pair*)realloc(peers, sizeof(ntp_assoc_status_pair)*npeers);
-               memcpy((void*)((ptrdiff_t)peers+peer_offset), (void*)req.data, sizeof(ntp_assoc_status_pair)*npeers);
+               if((tmp=realloc(peers, sizeof(ntp_assoc_status_pair)*npeers)) == NULL)
+                       free(peers), die(STATE_UNKNOWN, "can not (re)allocate 'peers' buffer\n");
+               peers=tmp;
+               memcpy((void*)((ptrdiff_t)peers+peer_offset), (void*)req.data, ntohs(req.count));
        } while(req.op&REM_MORE);
---------- 8< ----------------------------------------------------------

Could you test whether this fixes the problem for you?


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