[dpdk-dev] [PATCH v3 1/1] fbarray: get fbarrays from containerized secondary

[Burakov, Anatoly]

On 12-Jul-19 3:22 AM, Yasufumi Ogawa wrote:
> On 2019/07/11 22:14, Burakov, Anatoly wrote:
>> On 11-Jul-19 12:57 PM, Yasufumi Ogawa wrote:
>>> On 2019/07/11 19:53, Burakov, Anatoly wrote:
>>>> On 11-Jul-19 11:31 AM, yasufum.o at gmail.com wrote:
>>>>> From: Yasufumi Ogawa <ogawa.yasufumi at lab.ntt.co.jp>
>>>>>
>>>> <...>
>>>>
>>>>> +    if (getpid() == 1) {
>>>>> +        FILE *hn_fp;
>>>>> +        hn_fp = fopen("/etc/hostname", "r");
>>>>> +        if (hn_fp == NULL) {
>>>>> +            RTE_LOG(ERR, EAL,
>>>>> +                "Cannot open '/etc/hostname' for secondary\n");
>>>>> +            return -1;
>>>>> +        }
>>>>> +
>>>>> +        /* with docker, /etc/hostname just has one entry of 
>>>>> hostname */
>>>>> +        if (fscanf(hn_fp, "%s", proc_id) == EOF) {
>>>>
>>>> Apologies for not pointing this out earlier, but do i understand 
>>>> correctly that there's no bounds checking here, and fscanf() will 
>>>> write however many bytes it wants?
>>> I understand "%s" is not appropriate. hostname is 12 bytes char and I 
>>> thought proc_id[16] is enough, but it is unsafe. In addition, 
>>> hostname can be defined by user with docker's option, so it should be 
>>> enough for user defined name.
>>>
>>> How do you think expecting max 32 chars of hostname and set boundary 
>>> "%32s" as following?
>>>
>>>      proc_id[33];  /* define proc id from hostname less than 33 
>>> bytes. */
>>>      ...
>>>      if (fscanf(hn_fp, "%32s", proc_id) == EOF) {
>>>
>>
>> As long as it takes NULL-termination into account as well, it should 
>> be OK. I can't recall off the top of my head if %32s includes NULL 
>> terminator (probably not?).
> Do you agree if initialize with NULL chars to ensure proc_id is 
> NULL-terminated? As tested on my environment, "%Ns" sets next of Nth 
> char as NULL, but it seems more reliable.
>      proc_id[33] = { 0 };
> 
> Yasufumi
> 

Yes, that should be OK.

-- 
Thanks,
Anatoly