[Xymon] buffer overflow detected in xymongen (4.3.21)

Japheth Cleaver cleaver at terabithia.org
Tue Sep 29 19:40:32 CEST 2015

Hi Axel,

Would you be able to do a full BT on one of those core dumps? I'm not 
certain if Debian splits the debuginfo off into a separate package (like 
is done on the RH side), but that might need to be installed first.

Having the specific line this is coming from would make tracking down 
the root easier.

WML is indeed probably one of the more rarely used features nowadays, so 
it's quite possible there's a latent bug in there.


On 9/29/2015 10:27 AM, Axel Beckert wrote:
> Hi again,
> On Thu, Jul 02, 2015 at 03:49:17PM +0200, Axel Beckert wrote:
>> today our xymongen check went purple for about an hour. In the
>> xymongen.log I found tons of crash reports like this one:
>> *** buffer overflow detected ***: xymongen terminated
>> ======= Backtrace: =========
>> /lib/x86_64-linux-gnu/libc.so.6(+0x731ff)[0x7f31a13fc1ff]
>> /lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x37)[0x7f31a147f4c7]
>> /lib/x86_64-linux-gnu/libc.so.6(+0xf46e0)[0x7f31a147d6e0]
>> xymongen[0x40d526]
>> xymongen[0x403b72]
>> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5)[0x7f31a13aab45]
>> xymongen[0x40510c]
>> ======= Memory map: ========
> [...]
>> After ca. one hour it went yellow again [...]
> In the meanwhile I had cases where it took like 15 hours or so to
> recover.
>> Feel free to tell me what else could be helpful to track down this
>> bufferflow. I've found no (recent) core dump.
> In the meanwhile I gathered hundreds of core dumps, but the backtrace
> generated from them is not that helpful except for the exact
> commandline:
> [New LWP 104939]
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
> Core was generated by `xymongen --recentgifs --subpagecolumns=2 --wml --rss --nongreen-ignorecolumns=l'.
> Program terminated with signal SIGABRT, Aborted.
> #0  0x00007f96ef76a107 in __GI_raise (sig=sig at entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
> 56      ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
> ... because the error message...
>> "symlink nongreen.xml->index.wml failed: Transport endpoint is not
>> connected".
> ... comes from xymongen/wmlgen.c, i.e. I assume the buffer overflow is
> related to the generation of the WML view of Xymon as it would explain
> why nobody else suffered from it so far as this feature is probably
> rarely used nowadays.
> I'll also disable it for now in our setup to see if I'm right with my
> assumption about the source of the buffer overflow. But I still think
> it should be fixed if it's indeed in there.
> 		Kind regards, Axel Beckert

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