[Shapelib] Bug in DBFCloneEmpty

René Madsen madsen at neozone.com
Thu Jun 9 15:26:47 PDT 2005


Hi All

I identified a bug in DBFCloneEmpty

The lines to copy field type's states

   newDBF->pachFieldType = (char *) malloc ( sizeof(int) * psDBF->nFields );
   memcpy ( newDBF->pachFieldType, psDBF->pachFieldType, sizeof(int) *
psDBF->nFields );

However in shapelib.h pachFieldType defined as 

    char   *pachFieldType;

and in DBFOpen its initialised as 

    psDBF->pachFieldType = (char *) malloc(sizeof(char) * nFields);

and reallocated in DBFAddField as

    psDBF->pachFieldType = (char *) 
      SfRealloc( psDBF->pachFieldType, sizeof(char) * psDBF->nFields );

This causes a read overflow on psDBF->pachFieldType in memcpy that
occasionally generates an access violation.

A code change to  

   newDBF->pachFieldType = (char *) malloc ( sizeof(char) * psDBF->nFields
);
   memcpy ( newDBF->pachFieldType, psDBF->pachFieldType, sizeof(char) *
psDBF->nFields );

fixes the problem.



Regards

Rene Madsen

NeoZone A/S
Technical Director
Address: Amaliegade 16
DK-1256 K
Email: madsen at neozone.com
Tel office: +45 7020 6166
Fax: +45 3332 2291
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