Re: [PATCH] infiniband-diags: add rdma-ndd daemon

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 10/31/14 10:24, Weiny, Ira wrote:
>> On 10/31/14 00:54, ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org wrote:
>>   > +int read_and_set_hostname(int fd)
>>   > +{
>>   > +	int rc;
>>   > +	char buf[128];
>>   > +	if (read(fd, buf, 65) >= 0) {
>>   > +		buf[65] = '\0';
>>   > +		newline_to_null(buf);
>>   > +		strip_domain(buf);
>>   > +		syslog(LOG_INFO, "new hostname detected: %s", buf);
>>   > +		set_rdma_device_names((char *)buf);
>>   > +		rc = 0;
>>   > +	} else {
>>   > +		syslog(LOG_ERR, "Read %s Failed\n", SYS_HOSTNAME);
>>   > +		rc = -EIO;
>>   > +	}
>>   > +	return rc;
>>   > +}
>>
>> The above code will trigger reading uninitialized data if the data read from fd
>> is not newline-terminated and less than 65 characters are read.
>
> I'm not sure what you mean.  Do you mean "will trigger _using_ uninitialized data"?

Yes.

> How about the following?
>
> @@ -155,8 +156,8 @@ int read_and_set_hostname(int fd)
>   {
>          int rc;
>          char buf[128];
> -       if (read(fd, buf, 65) >= 0) {
> -               buf[65] = '\0';
> +       memset(buf, 0, sizeof(buf));
> +       if (read(fd, buf, 64) >= 0) {
>                  newline_to_null(buf);
>                  strip_domain(buf);
>                  syslog(LOG_INFO, "new hostname detected: %s", buf);

This change looks fine to me. A possible alternative is to use dup() + 
fdopen() + fgets() + fclose(). fgets() namely automatically appends a 
terminating '\0'.

Bart.

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