Re: [dpdk-dev] [PATCH v1 2/3] net/hyperv: implement core functionality

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 18 Dec 2017 17:46:23 +0100
Adrien Mazarguil <adrien.mazarguil@6wind.com> wrote:

> +static int
> +ether_addr_from_str(struct ether_addr *eth_addr, const char *str)
> +{
> +	static const uint8_t conv[0x100] = {
> +		['0'] = 0x80, ['1'] = 0x81, ['2'] = 0x82, ['3'] = 0x83,
> +		['4'] = 0x84, ['5'] = 0x85, ['6'] = 0x86, ['7'] = 0x87,
> +		['8'] = 0x88, ['9'] = 0x89, ['a'] = 0x8a, ['b'] = 0x8b,
> +		['c'] = 0x8c, ['d'] = 0x8d, ['e'] = 0x8e, ['f'] = 0x8f,
> +		['A'] = 0x8a, ['B'] = 0x8b, ['C'] = 0x8c, ['D'] = 0x8d,
> +		['E'] = 0x8e, ['F'] = 0x8f, [':'] = 0x40, ['-'] = 0x40,
> +		['\0'] = 0x60,
> +	};
> +	uint64_t addr = 0;
> +	uint64_t buf = 0;
> +	unsigned int i = 0;
> +	unsigned int n = 0;
> +	uint8_t tmp;
> +
> +	do {
> +		tmp = conv[(int)*(str++)];

Cast to int will cause out of bounds reference on non-ascii strings.
The parser will get confused by:
    001:aa:bb:cc:dd:ee:ff or invalid strings.

Why not use sscanf which would be safer in this case.


/**
 * Parse 48bits Ethernet address in pattern xx:xx:xx:xx:xx:xx.
 *
 * @param eth_addr
 *   A pointer to a ether_addr structure.
 * @param str
 *   A pointer to string contains the formatted MAC address.
 * @return
 *   0 if the address is valid
 *  -EINVAL if address is not formatted properly
 */
static inline int
ether_parse_addr(struct ether_addr *eth_addr, const char *str)
{
	int n;
	
	n = sscanf(str, 
		   "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx",
		   &eth_addr->addr_bytes[0],
		   &eth_addr->addr_bytes[1],
		   &eth_addr->addr_bytes[2],
		   &eth_addr->addr_bytes[3],
		   &eth_addr->addr_bytes[4],
		   &eth_addr->addr_bytes[5]);
	return (n == ETHER_ADDR_LEN) ? 0 : -EINVAL;
}

> +		if (!tmp)
> +			return -EINVAL;
> +		if (tmp & 0x40) {
> +			i += (i & 1) + (!i << 1);
> +			addr = (addr << (i << 2)) | buf;
> +			n += i;
> +			buf = 0;
> +			i = 0;
> +		} else {
> +			buf = (buf << 4) | (tmp & 0xf);
> +			++i;
> +		}
> +	} while (!(tmp & 0x20));
> +	if (n > 12)
> +		return -EINVAL;
> +	i = RTE_DIM(eth_addr->addr_bytes);
> +	while (i) {
> +		eth_addr->addr_bytes[--i] = addr & 0xff;
> +		addr >>= 8;
> +	}
> +	return 0;
> +}
> +