[CRIU] [PATCH v7 01/15] sysctl: add CTL_FLAGS_HAS to mark successful sysctl_op request

[Pavel Tikhomirov]

On 05/06/2016 03:37 PM, Pavel Emelyanov wrote:
> On 05/06/2016 03:10 PM, Pavel Tikhomirov wrote:
>> On 05/06/2016 02:47 PM, Pavel Emelyanov wrote:
>>> On 04/28/2016 07:38 PM, Pavel Tikhomirov wrote:
>>>> v4: replace separate has pointer to CTL_FLAGS_HAS flag, second part in
>>>> patch "net/ipv4: add net_conf_op to reuse for ipv6"
>>>> v6: define CTL_FLAGS_HAS
>>>> v7: also allow EIO on do_sysctl_op for optional sysctls like
>>>> stable_secret and fix sysctl file to close in error path
>>>
>>> Wait a second. If we've managed to open a sysctl file, but failed to write into
>>> it, why should we pretend as if there was not this sysctl at all?
>>
>> Now we only set CTL_FLAGS_OPTIONAL for op == CTL_READ. So it meant to
>> be: if we opened sysctl but failed to read it, it is in
>> not-yet-initialized state and we can skip it safely.
>
> I'm not sure that treating _any_ systl like this will work. Can you shed
> more light on what's the issue with stable_secret sysctl is?

In addrconf_sysctl_stable_secret:

if (!write && !secret->initialized) {
         err = -EIO;
         goto out;
}

[root at dhcp-10-30-24-224 ~]# cat /proc/sys/net/ipv6/conf/lo/stable_secret
cat: /proc/sys/net/ipv6/conf/lo/stable_secret: Input/output error
[root at dhcp-10-30-24-224 ~]# echo 
"2607:f0d0:1002:0051:0000:0000:0000:0004" > 
/proc/sys/net/ipv6/conf/lo/stable_secret
[root at dhcp-10-30-24-224 ~]# cat /proc/sys/net/ipv6/conf/lo/stable_secret
2607:f0d0:1002:0051:0000:0000:0000:0004

So these sysctl should be first initialized and only after one can read it.

>
>> Will adding an implicit op-check here be satisfactory?
>>
>>>
>>>>
>>>> https://jira.sw.ru/browse/PSBM-30942
>>>>
>>>> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
>>>> ---
>>>>  criu/include/sysctl.h |  1 +
>>>>  criu/sysctl.c         | 21 +++++++++++++++++----
>>>>  2 files changed, 18 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/criu/include/sysctl.h b/criu/include/sysctl.h
>>>> index b949a40..3611ef1 100644
>>>> --- a/criu/include/sysctl.h
>>>> +++ b/criu/include/sysctl.h
>>>> @@ -35,5 +35,6 @@ enum {
>>>>   * Some entries might be missing mark them as optional.
>>>>   */
>>>>  #define CTL_FLAGS_OPTIONAL	1
>>>> +#define CTL_FLAGS_HAS		2
>>>>
>>>>  #endif /* __CR_SYSCTL_H__ */
>>>> diff --git a/criu/sysctl.c b/criu/sysctl.c
>>>> index 21ae4ce..60e52db 100644
>>>> --- a/criu/sysctl.c
>>>> +++ b/criu/sysctl.c
>>>> @@ -303,8 +303,13 @@ static int __userns_sysctl_op(void *arg, int proc_fd, pid_t pid)
>>>>  		close(nsfd);
>>>>
>>>>  		for (i = 0; i < userns_req->nr_req; i++) {
>>>> -			if (do_sysctl_op(fds[i], reqs[i], op) < 0)
>>>> -				exit(1);
>>>> +			if (do_sysctl_op(fds[i], reqs[i], op) < 0) {
>>>> +				if (errno != EIO || !(req->flags & CTL_FLAGS_OPTIONAL))
>>>> +					exit(1);
>>>> +			} else {
>>>> +				/* mark sysctl in question exists */
>>>> +				req->flags |= CTL_FLAGS_HAS;
>>>> +			}
>>>>  		}
>>>>
>>>>  		exit(0);
>>>> @@ -372,8 +377,16 @@ static int __nonuserns_sysctl_op(struct sysctl_req *req, size_t nr_req, int op)
>>>>  		}
>>>>
>>>>  		ret = do_sysctl_op(fd, req, op);
>>>> -		if (ret)
>>>> -			goto out;
>>>> +		if (ret) {
>>>> +			if (errno != EIO || !(req->flags & CTL_FLAGS_OPTIONAL)) {
>>>> +				close(fd);
>>>> +				goto out;
>>>> +			}
>>>> +		} else {
>>>> +			/* mark sysctl in question exists */
>>>> +			req->flags |= CTL_FLAGS_HAS;
>>>> +		}
>>>> +
>>>>  		close(fd);
>>>>  		req++;
>>>>  	}
>>>>
>>>
>> .
>>
>