[CRIU] [PATCH] util: disable log service in cr_system_userns if error fd was -1

[Stanislav Kinsburskiy]

22.04.2016 18:16, Pavel Emelyanov пишет:
> On 04/22/2016 07:02 PM, Stanislav Kinsburskiy wrote:
>>
>> 22.04.2016 17:58, Pavel Emelyanov пишет:
>>> On 04/22/2016 06:23 PM, Stanislav Kinsburskiy wrote:
>>>> In case of error fd was negative, log_fd is _moved_ as STDERR for the child.
>>>> After move, log_fd is closed, and thus log service is broken and any error
>>>> prints will disappear.
>>>> This patch disables log service, thus redirecting error output to STDERR
>>>> (which is log fd in this case).
>>>>
>>>> Calling of log fini is:
>>>> 1) to early: reopen_fd_as_nocheck will fail
>>>> 2) to much: close_safe will print error message, because log fd was already
>>>> closed
>>>>
>>>> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
>>>> ---
>>>>    criu/util.c |    6 +++---
>>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/criu/util.c b/criu/util.c
>>>> index dae6031..12ce8b4 100644
>>>> --- a/criu/util.c
>>>> +++ b/criu/util.c
>>>> @@ -641,9 +641,6 @@ int cr_system_userns(int in, int out, int err, char *cmd,
>>>>    		    move_img_fd(&err, STDIN_FILENO))
>>>>    			goto out_chld;
>>>>    
>>>> -		if (stop_log_fd)
>>>> -			log_fini();
>>>> -
>>>>    		if (in < 0) {
>>>>    			close(STDIN_FILENO);
>>>>    		} else {
>>>> @@ -660,6 +657,9 @@ int cr_system_userns(int in, int out, int err, char *cmd,
>>>>    		if (reopen_fd_as_nocheck(STDERR_FILENO, err))
>>>>    			goto out_chld;
>>>>    
>>>> +		if (stop_log_fd)
>>>> +			clear_bit(LOG_FD_OFF, sfd_map);
>>> Messing directly with sfd_map here is bad idea. Add call __log_fini()
>>> that finis the log with dead file descriptor.
>> The problem here is not in log_fini(), but in close_service_fd(). Even
>> in close_safe(), to be precise.
>> What if I add check for valid fd to close_safe()?
> No. You just need to unmark service fd that has the fd closed, right?
> Make special funciton for this and call it here. It's just to keep
> the API clear.

This special function will look like this:

void __log_fini(void)
{
         int fd;

         fd = get_service_fd(LOG_FD_OFF);
         if (fd < 0)
                 return 0;

         clear_bit(type, sfd_map);
         return 0;
}

Is it ok?