[mapserver-users] MapServer segfaults when processing GetFeatureInfo

[Mark Phillips]

I am having a very bizarre problem with MapServer and GetFeatureInfo
requests, and I'm wondering if anyone has had similar problems and/or has
ideas about how to address it.

I have a raster layer (actually, a bunch of them) where MapServer sometimes
segfaults when serving a GetFeatureInfo request, depending on the
coordinate of the point being queried.  I have come up with a couple of
test cases, which are exactly identical to each other except for the value
of X in the GetFeatureInfo request.  In one case, X=913, and MapServer
 correctly processes the GetFeatureInfo request and returns correct
results.  In the other case, X=912, and MapServer segfaults.  Both of these
values of X are valid, and both  correspond to pixels in the image where
MapServer correctly displays the raster in question when called with a
GetMap request.

My hunch is that the problem might be related to a misconfiguration of
MapServer on my part, or a misconfiguration of the projections involved.
 The layer data is in a LAEA projection, and due to constraints on this
project that are beyond my control, I have MapServer reprojecting it to a
bizarre web mercator projection (EPSG 3857, aka EPSG 3785) for output,
so the GetFeatureInfo request is expressed in EPSG 3857.  But I'm stumped
as to what the problem could be, and having MapServer crash with a
segmentation fault seems like an indication of some kind of bug, even if
I've got a configuration error.

I've tried turning on debugging in the mapfile, but nothing useful shows up
in the log file.

I've also tested this with several versions of MapServer, including 6.0.3
and 6.2-beta1, with the same results.  I'm running these tests on a CentOS
6.2 system, compiling MapServer with the options --with-proj --with-ogr
--with-gdal --with-wfs --with-wcs --with-wms --with-wmsclient
--with-wfsclient and --with-php=/usr/include/php, and using gdal 1.7.2 and
proj 4.7.0.

If you have any thoughts about what the problem could be, I'd love to hear
from you!  I'll append my mapfile below, along with the two test requests I
mentioned above.

The layer data file that I am using is too big to attach to this email, but
I've created a tgz file containing everything needed to run my tests -- the
mapfile, layer file, and test script; you can download it here:

      http://rain.nemac.org/~mbp/mapserver-gfi-problem.tgz

If anyone wants to download this and try it with your copy of MapServer,
let me know whether you get the same results that I'm getting!

Thanks in advance!

--Mark

Here is the mapfile I am using:

MAP
  CONFIG "MS_ERRORFILE" "mapserver.log"
  DEBUG 5
  PROJECTION
    "init=epsg:3857"
  END
  WEB
    HEADER "./dummy_template"
    FOOTER "./dummy_template"
    METADATA
      "ows_enable_request"     "*"
      "wms_srs"                "EPSG:3857"
    END
  END
  LAYER
    NAME layer1
    PROJECTION
      "+proj=laea"
      "+lat_0=45"
      "+lon_0=-100"
      "+x_0=0"
      "+y_0=0"
      "+a=6370997"
      "+b=6370997"
      "+units=m"
      "+no_defs"
    END
    TYPE     RASTER
    DUMP     TRUE
    STATUS   OFF
    DATA     layer1.tif
    HEADER   ./dummy_template
    TEMPLATE ./dummy_template
    METADATA
      "wms_title"             "layer1"
      "wms_abstract"          "layer1"
      "gml_include_items"     "value_0"
    END
  END
END


And here are the two query strings for the two test cases:

    this one runs correctly:

map=./mapfile.map&TRANSPARENT=true&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetFeatureInfo&STYLES=&FORMAT=image/png&INFO_FORMAT=application/vnd.ogc.gml&BBOX=-11859604.53136514,4696887.582602486,-11830673.11615924,4710053.860724591&CRS=EPSG:3857&LAYERS=layer1&QUERY_LAYERS=layer1&WIDTH=1514&HEIGHT=689&X=913&Y=334

    this one causes a seg fault:

map=./mapfile.map&TRANSPARENT=true&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetFeatureInfo&STYLES=&FORMAT=image/png&INFO_FORMAT=application/vnd.ogc.gml&BBOX=-11859604.53136514,4696887.582602486,-11830673.11615924,4710053.860724591&CRS=EPSG:3857&LAYERS=layer1&QUERY_LAYERS=layer1&WIDTH=1514&HEIGHT=689&X=912&Y=334
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/mapserver-users/attachments/20120718/e94c1bf5/attachment.html>