On 12/05, Paul Moore wrote:
>
> On Thursday, December 05, 2013 05:59:53 PM Oleg Nesterov wrote:
> >
> > Note: perhaps we should simply kill ptrace_parent(), it buys
> > almost nothing and it is obviously racy. Or perhaps we should
> > change it to ensure it can't wrongly return the natural parent
> > if it races with ptrace_detach.
>
> Can you elaborate on "kill ptrace_parent()"? If the process is being traced
> we do need to fetch the tracer's task_struct for use in the SELinux access
> check at this bottom of the diff below. If you have something better in mind
> than ptrace_parent() it would be helpful to share that ...
Sorry for confusion.
I meant that the code like
tracer = ptrace_parent(p);
if (tracer)
do_something(tracer);
doesn't look better than just
if (p->ptrace)
do_something(p->parent);
but this is subjective of course.
And perhaps I am wrong. Because otoh the usage of ->ptrace should be
avoided outside of the core kernel code.
Mostly it annoys me because it is racy, without tasklist_lock it can
return ->real_parent (which never traced its child) if it races with
attach or detach, and I do not see a simple fix.
Oleg.
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