Code:  findoprnd(ITEM *ptr, int32 *pos)
 {
 	if (ptr[*pos].type == VAL || ptr[*pos].type == VALTRUE)
 	{
 		ptr[*pos].left = 0;
		(*pos)++;
	}
	else if (ptr[*pos].val == (int32) '!')
	{
		ptr[*pos].left = 1;
		(*pos)++;
		findoprnd(ptr, pos);
	}
	else
	{
		ITEM	   *curitem = &ptr[*pos];
		int32		tmp = *pos;

		(*pos)++;
		findoprnd(ptr, pos);
		curitem->left = *pos - tmp;
		findoprnd(ptr, pos);
	}
}

Commit Message: Predict integer overflow to avoid buffer overruns.

Several functions, mostly type input functions, calculated an allocation
size such that the calculation wrapped to a small positive value when
arguments implied a sufficiently-large requirement.  Writes past the end
of the inadvertent small allocation followed shortly thereafter.
Coverity identified the path_in() vulnerability; code inspection led to
the rest.  In passing, add check_stack_depth() to prevent stack overflow
in related functions.

Back-patch to 8.4 (all supported versions).  The non-comment hstore
changes touch code that did not exist in 8.4, so that part stops at 9.0.

Noah Misch and Heikki Linnakangas, reviewed by Tom Lane.

Security: CVE-2014-0064
CWE ID: CWE-189
 findoprnd(ITEM *ptr, int32 *pos)
 {
	/* since this function recurses, it could be driven to stack overflow. */
	check_stack_depth();

 	if (ptr[*pos].type == VAL || ptr[*pos].type == VALTRUE)
 	{
 		ptr[*pos].left = 0;
		(*pos)++;
	}
	else if (ptr[*pos].val == (int32) '!')
	{
		ptr[*pos].left = 1;
		(*pos)++;
		findoprnd(ptr, pos);
	}
	else
	{
		ITEM	   *curitem = &ptr[*pos];
		int32		tmp = *pos;

		(*pos)++;
		findoprnd(ptr, pos);
		curitem->left = *pos - tmp;
		findoprnd(ptr, pos);
	}
}
