On 8/20/19 8:10 AM, Carlos Antonio Neira Bustos wrote:
> Hi Yonghong,
>
> Thanks for taking the time to review this.
>
>
>>> + *
>>> + * **-EINVAL** if *size_of_pidns* is not valid or unable to get ns, pid
>>> + * or tgid of the current task.
>>> + *
>>> + * **-ECHILD** if /proc/self/ns/pid does not exists.
>>> + *
>>> + * **-ENOTDIR** if /proc/self/ns does not exists.
>>
>> Let us remove ECHILD and ENOTDIR and replace it with ENOENT as I
>> described below.
>>
>> Please *do verify* what happens when namespaces or pid_ns are not
>> configured.
>>
>
>
> I have tested kernel configurations without namespace support and with
> namespace support but without pid namespaces, the helper returns -EINVAL
> on both cases, now it should return -ENOENT.
Indeed. -ENOENT is better.
>
>
>>> +struct bpf_pidns_info {
>>> + __u32 dev;
>>
>> Please add a comment for dev for how device major and minor number are
>> derived. User space gets device major and minor number, they need to
>> compare to the corresponding major/minor numbers returned by this helper.
>>
>>> + __u32 nsid;
>>> + __u32 tgid;
>>> + __u32 pid;
>>> +};
>>
>
> What do you think of this comment ?
>
> struct bpf_pidns_info {
> __u32 dev; /* major/minor numbers from /proc/self/ns/pid.
> * User space gets device major and minor numbers from
> * the same device that need to be compared against the
> * major/minor numbers returned by this helper.
> */
> __u32 nsid;
> __u32 tgid;
> __u32 pid;
> };
>
To be more specific, I like a comment similar to below in uapi bpf.h
struct bpf_cgroup_dev_ctx {
/* access_type encoded as (BPF_DEVCG_ACC_* << 16) |
BPF_DEVCG_DEV_* */
__u32 access_type;
__u32 major;
__u32 minor;
};
Some like:
/* dev encoded as (major << 8 | (minor & 0xff)) */
>>
>> Please put an empty line. As a general rule for readability,
>> put an empty line if control flow is interrupted, e.g., by
>> "return", "break" or "continue". At least this is what
>> I saw most in bpf mailing list.
>>
> I'll fix it in version 10.
>
>>> + len = strlen(pidns_path) + 1;
>>> + memcpy((char *)tmp->name, pidns_path, len);
>>> + tmp->uptr = NULL;
>>> + tmp->aname = NULL;
>>> + tmp->refcnt = 1;
>>> + ret = filename_lookup(AT_FDCWD, tmp, 0, &kp, NULL);
>> Adding below to free kmem cache memory
>> kmem_cache_free(names_cachep, fname);
>>
>
> I think we don't need to call kmem_cache_free as filename_lookup
> calls putname that calls kmem_cache_free.
Oh, right. Thanks for checking this.
>
>
> Thanks a lot for your help.
>
> Bests
>
>> In the above, we checked task_active_pid_ns().
>> If not returning NULL, we have a valid pid ns. So the above
>> filename_lookup should not go wrong. We can still keep
>> the error checking though.
>>
>>> + if (ret) {
>>> + memset((void *)pidns_info, 0, (size_t) size);
>>> + return ret;
>>
>>
>
> I think we could get rid of this.
>
>
