On 26.04.2017 19:11, Kirill Tkhai wrote:
> On 26.04.2017 18:53, Oleg Nesterov wrote:
>> On 04/17, Kirill Tkhai wrote:
>>>
>>> +struct pidns_ioc_req {
>>> +/* Set vector of last pids in namespace hierarchy */
>>> +#define PIDNS_REQ_SET_LAST_PID_VEC 0x1
>>> + unsigned int req;
>>> + void __user *data;
>>> + unsigned int data_size;
>>> + char std_fields[0];
>>> +};
>>
>> see below,
>>
>>> +static long set_last_pid_vec(struct pid_namespace *pid_ns,
>>> + struct pidns_ioc_req *req)
>>> +{
>>> + char *str, *p;
>>> + int ret = 0;
>>> + pid_t pid;
>>> +
>>> + read_lock(&tasklist_lock);
>>> + if (!pid_ns->child_reaper)
>>> + ret = -EINVAL;
>>> + read_unlock(&tasklist_lock);
>>> + if (ret)
>>> + return ret;
>>
>> why do you need to check ->child_reaper under tasklist_lock? this looks pointless.
>>
>> In fact I do not understand how it is possible to hit pid_ns->child_reaper == NULL,
>> there must be at least one task in this namespace, otherwise you can't open a file
>> which has f_op == ns_file_operations, no?
>
> Sure, it's impossible to pick a pid_ns, if there is no the pid_ns's tasks. I added
> it under impression of
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=dfda351c729733a401981e8738ce497eaffcaa00
> but here it's completely wrong. It will be removed in v2.
>
>>> + if (req->data_size >= PAGE_SIZE)
>>> + return -EINVAL;
>>> + str = vmalloc(req->data_size + 1);
>>
>> then I don't understand why it makes sense to use vmalloc()
>>
>>> + if (!str)
>>> + return -ENOMEM;
>>> + if (copy_from_user(str, req->data, req->data_size)) {
>>> + ret = -EFAULT;
>>> + goto out_vfree;
>>> + }
>>> + str[req->data_size] = '\0';
>>> +
>>> + p = str;
>>> + while (p && *p != '\0') {
>>> + if (!ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN)) {
>>> + ret = -EPERM;
>>> + goto out_vfree;
>>> + }
>>> +
>>> + if (sscanf(p, "%d", &pid) != 1 || pid < 0 || pid > pid_max) {
>>> + ret = -EINVAL;
>>> + goto out_vfree;
>>> + }
>>
>> Well, this is ioctl(), do we really want to parse the strings?
>>
>> Can't we make
>>
>> struct pidns_ioc_req {
>> ...
>> int nr_pids;
>> pid_t pids[0];
>> }
>>
>> and just use get_user() in a loop? This way we can avoid vmalloc() or anything
>> else altogether.
>
> Since it's a generic structure for different types of the requests, it may be extended
> in the future. We won't be able to add new fields, if we compose the structure the way
> you suggested, will we?
Though, we may go this way if just do the fields generic:
struct pidns_ioc_req {
unsigned int req;
unsigned int data_size;
union {
pid_t pid[0];
};
};
Ok, I'll rework the patchset in this way.
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