valid_length(uint8_t option, int dl, int *type)
{
 const struct dhcp_opt *opt;
 ssize_t sz;

 if (dl == 0)
 return -1;

 for (opt = dhcp_opts; opt->option; opt++) {
 if (opt->option != option)
 continue;

 
 		if (type)
 			*type = opt->type;
		/* The size of RFC3442 and RFC5969 options is checked at a later
		 * stage in the code */
 		if (opt->type == 0 ||
 		    opt->type & (STRING | RFC3442 | RFC5969))
 			return 0;
		/* The code does not use SINT16 / SINT32 together with ARRAY.
		 * It is however far easier to reason about the code if all
		 * possible array elements are included, and also does not code
		 * any additional CPU resources. sizeof(uintXX_t) ==
		 * sizeof(intXX_t) can be assumed. */
 		sz = 0;
		if (opt->type & (UINT32 | SINT32 | IPV4))
 			sz = sizeof(uint32_t);
		else if (opt->type & (UINT16 | SINT16))
 			sz = sizeof(uint16_t);
		else if (opt->type & UINT8)
 			sz = sizeof(uint8_t);
		if (opt->type & ARRAY) {
			/* The result of modulo zero is undefined. There are no
			 * options defined in this file that do not match one of
			 * the if-clauses above, so the following is not really
			 * necessary. However, to avoid confusion and unexpected
			 * behavior if the defined options are ever extended,
			 * returning false here seems sensible. */
			if (!sz) return -1;
			return (dl % sz == 0) ? 0 : -1;
		}
		return (sz == dl) ? 0 : -1;
 	}
 
 	/* unknown option, so let it pass */
 return 0;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.