On 29/08/2019 05:47, Florian Weimer wrote:
* 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?
Do we really need that ad-hoc support on tst-pldd to make it support
ptrace_scope 1?
I don't oppose the support Stefan has added on latest iteration to
make it work, but this is a lot of code to support a very specific
scenario...