Re: systemtap broken by USER_NS for now

[David Smith <dsmith at redhat dot com>]

On 05/22/2013 04:40 PM, David Smith wrote:
> On 05/22/2013 09:00 AM, Alexander Y. Fomichev wrote:
>> Hi
>>
>> for now user_ns unconditionally requires
>> CONFIG_UIDGID_STRICT_TYPE_CHECKS and the latter in turn breaks things
>> this way:
>>
>> typedef struct {
>>         uid_t val;
>> } kuid_t;
>>
>> and so:
>>
>> stap # ./probe.stp
>> In file included from /usr/share/systemtap/runtime/linux/task_finder.c:17:0,
>>                  from /usr/share/systemtap/runtime/linux/runtime.h:188,
>>                  from /usr/share/systemtap/runtime/runtime.h:24,
>>                  from
>> /tmp/.private/root/stap7M7WmA/stap_6ce999ddb8d32c70dcbe287153f6957f_16537_src.c:22:
>> /usr/share/systemtap/runtime/linux/task_finder2.c: In function
>> '__stp_utrace_attach_match_filename':
>> /usr/share/systemtap/runtime/linux/task_finder2.c:816:11: error:
>> incompatible types when assigning to type 'uid_t' from type 'kuid_t'
>>   tsk_euid = task_euid(tsk);
>>            ^
>> .....................................................................
>>
>> It seems like fix is straightforward - just use from_kuid_munged to
>> get euid if CONFIG_UIDGID_STRICT_TYPE_CHECKS is defined. (really it
>> always works on latest kernels but breaks older ones). I've attached a
>> simple patch and it works for 3.9 (both with and without
>> STRICT_TYPE_CHECKS) but i'm not systemtap guy so i could be completely
>> wrong. Feel free to throw it out without reading :)
>>
>> --
>> Best regards.
>>        Alexander Y. Fomichev <git.user@gmail.com>
>>
> 
> Hmm, thanks for finding this and developing the patch. The tricky part
> here will be supporting 3.9 without breaking some of the earliest
> kernels we support (like RHEL4's 2.6.9).
> 
> I'll look into your patch. I'm also wondering if some of the procfs
> fixes I just put in will work with CONFIG_UIDGID_STRICT_TYPE_CHECKS.
> 
> I'll send out an update when I've figured something out.

I've checked your (a bit modified) work in as commit 8571631. As I
feared, I had to tweak it a bit to handle old kernels.

Thanks again.

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)