[Devel] [PATCH] ve: allow to do anything from init_user_ns

[Stanislav Kinsburskiy]

25.07.2017 14:46, Konstantin Khorenko пишет:
> The only possible problem i can see here in the future:
> imagine we implement n:m mapping for user namespaces of vz Containers,
> after that each fs superblock will contain a link to user_ns in which it was created
> (in order to get user_ns id mapping).
> 
> Thus in case someone enters from host to Container mount namespace and mount something,
> most probably it won't be accessible inside a Container due to different uid/gid mappings for file owners.
> 

Whom it might be?

> -- 
> Best regards,
> 
> Konstantin Khorenko,
> Virtuozzo Linux Kernel Team
> 
> On 07/24/2017 11:55 PM, Andrei Vagin wrote:
>> From: Andrei Vagin <avagin at virtuozzo.com>
>>
>> current_user_ns_initial() is used to restrict operations,
>> which are allowed in a ve initial userns, but aren't allowed
>> in sub-user-namespaces. But now this function doesn't take
>> into account init_user_ns. init user_ns is a root item in the
>> hierarchy of user namespaces, so it is actually initiall
>> for ve-s. The upstream kernel allow to do anything from
>> init_user_ns, and we don't want to change this behaviour.
>>
>> https://jira.sw.ru/browse/PSBM-58574
>>
>> Cc: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
>> Cc: Kirill Tkhai <ktkhai at virtuozzo.com>
>> Signed-off-by: Andrei Vagin <avagin at virtuozzo.com>
>> ---
>>  kernel/ve/ve.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
>> index 0533d79..e95b3f3 100644
>> --- a/kernel/ve/ve.c
>> +++ b/kernel/ve/ve.c
>> @@ -241,6 +241,9 @@ bool current_user_ns_initial(void)
>>      struct ve_struct *ve = get_exec_env();
>>      bool ret = false;
>>
>> +    if (current_user_ns() == &init_user_ns)
>> +        return true;
>> +
>>      rcu_read_lock();
>>      if (ve->ve_ns && ve->init_cred->user_ns == current_user_ns())
>>          ret = true;
>>