[PATCH] Add UNSUPPORTED check in elf/tst-pldd.
Florian Weimer
fweimer@redhat.com
Thu Aug 29 08:47:00 GMT 2019
* Stefan Liebler:
> On 8/28/19 11:24 AM, Florian Weimer wrote:
>> * Stefan Liebler:
>>
>>> static void
>>> target_process (void *arg)
>>> {
>>> + if (ptrace_scope == 1)
>>> + {
>>> + /* YAMA is configured to "restricted ptrace".
>>> + Disable the restriction for this subprocess. */
>>> + support_ptrace_process_set_ptracer_any ();
>>> + }
>>> +
>>> pause ();
>>> }
>>
>> I think this has a race condition if pldd attaches to the process before
>> the support_ptrace_process_set_ptracer_any call. I have no idea how
>> hard it is in practice to hit this race. It should be possible to use a
>> process-shared barrier or some other form of synchronization to avoid
>> this issue.
>>
>> Thanks,
>> Florian
>>
>
> I've added a synchronization with stdatomic.h on a shared memory mapping.
> I've not used pthread* functions as I don't want to link against
> libpthread.so. Then further adjustments are needed.
>
> Or should I just restrict the test ptrace_scope 0 as Adhemerval has
> proposed in his post?
Is it possible to create a process tree like this?
parent (performs output checks)
subprocess 1 (becomes pldd via execve)
subprocess 2
If you execve pldd from subprocess 1, wouldn't subprocess 2 in its
ptrace scope for ptrace_scope < 2?
Thanks,
Florian
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