Messages in this thread | | | Date | Fri, 6 Dec 2013 15:47:35 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] selinux: selinux_setprocattr()->ptrace_parent() needs rcu_read_lock() |
| |
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.
| |