[Devel] Re: [PATCH 1/1] implement s390 clone_with_pids syscall

[Serge E. Hallyn]

Quoting Nathan Lynch (nathanl at austin.ibm.com):
> 
> > +	parent_tid_ptr = (int *)kca.parent_tid_ptr;
> > +	child_tid_ptr =  (int *)kca.child_tid_ptr;
> > +
> > +	stack_size = (unsigned long)kca.child_stack_size;
> > +	child_stack = (unsigned long)kca.child_stack_base;
> > +	if (child_stack)
> > +		child_stack += stack_size;
> 
> Should this calculation not be of the form:
> child_stack = arch_dependent_alignment(child_stack + stack_size - 1)
> ?
> 
> Is overflow a concern?
> 
> Same questions apply to the x86 version.

Hmm...  if the stack isn't valid, the task will just segfault, so
it's not dangerous for the kernel, right?  Note that for instance
arch/s390/kernel/process.c:SYS_clone() doesn't check the validity
of the new stack pointer passed in either.

-serge
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