Re: [dpdk-dev] [PATCH v1 1/1] cmdline: add any multi string mode to token string

[Olivier Matz <olivier.matz@6wind.com>]

Hi Piotr,

This is globally ok for me. Please see a comment below.

On 04/01/2016 01:36 PM, Piotr Azarewicz wrote:
> @@ -162,12 +174,15 @@ cmdline_parse_string(cmdline_parse_token_hdr_t *tk, const char *buf, void *res,
>  	}
>  
>  	if (res) {
> -		/* we are sure that token_len is < STR_TOKEN_SIZE-1 */
> -		snprintf(res, STR_TOKEN_SIZE, "%s", buf);
> -		*((char *)res + token_len) = 0;
> +		if ((sd->str != NULL) && (strcmp(sd->str, TOKEN_STRING_MULTI) == 0))
> +			snprintf(res, token_len + 1, "%s", buf);
> +		else {
> +			/* we are sure that token_len is < STR_TOKEN_SIZE-1 */
> +			snprintf(res, STR_TOKEN_SIZE, "%s", buf);
> +			*((char *)res + token_len) = 0;
> +		}
>  	}
>  

Using token_len + 1 as the buffer size in the snprintf looks a
bit dangerous, as it won't protect from overflows.

See the following example:


struct cmd_foo_result {
	cmdline_fixed_string_t args;
        cmdline_fixed_string_t foo;
};

static void
cmd_foo_parsed(void *parsed_result,
        __rte_unused struct cmdline *cl,
        __rte_unused void *data)
{
        struct cmd_foo_result *res = parsed_result;
        printf("foo=%s, args=%s\n", res->foo, res->args);
}

cmdline_parse_token_string_t cmd_foo_foo =
        TOKEN_STRING_INITIALIZER(struct cmd_foo_result, foo,
                                 "foo");
cmdline_parse_token_string_t cmd_foo_args =
        TOKEN_STRING_INITIALIZER(struct cmd_foo_result, args,
                TOKEN_STRING_MULTI);

cmdline_parse_inst_t cmd_foo = {
        .f = cmd_foo_parsed,  /* function to call */
        .data = NULL,      /* 2nd arg of func */
        .help_str = "test",
        .tokens = {        /* token list, NULL terminated */
                (void *)&cmd_foo_foo,
                (void *)&cmd_foo_args,
                NULL,
        },
};


The result will be:

# ok
RTE>>foo xxx
foo=foo, args=xxx

# not ok, args overflows in foo
RTE>>foo
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
foo=xxxxxxxxxxxxxxxxxxxxxxx,
args=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx


That's why snprintf() should still use STR_TOKEN_SIZE.


Regards,
Olivier