[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20090506224650.GZ3036@sequoia.sous-sol.org>
Date: Wed, 6 May 2009 15:46:50 -0700
From: Chris Wright <chrisw@...s-sol.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Chris Wright <chrisw@...s-sol.org>,
Roland McGrath <roland@...hat.com>,
linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>
Subject: Re: [PATCH 3/3] ptrace: do not use task_lock() for attach
* Oleg Nesterov (oleg@...hat.com) wrote:
> + write_lock_irq(&tasklist_lock);
> retval = -EPERM;
> if (unlikely(task->exit_state))
> - goto bad;
> + goto unlock_tasklist;
> if (task->ptrace)
> - goto bad;
> + goto unlock_tasklist;
So, task->ptrace now protected by tasklist_lock to keep concurrent tracers
from both attaching to same task? What does this do for setprocattr()?
task_lock(p);
tracer = tracehook_tracer_task(p);
if (tracer)
ptsid = task_sid(tracer);
task_unlock(p);
Looks like it is racy.
cpu1 (tracer) cpu2 (tracee, changing sid)
------------- ---------------------------
task_lock(tracee);
__ptrace_may_access(tracee, ATTACH);
task_unlock(tracee);
task_lock(tracee)
<security check passes> tracer = tracehook_tracer_task(tracee);
if (tracer) <-- NULL, !tracee->ptrace
...
update sid w/out checking against tracer
write_lock_irq(&tasklist_lock);
...
tracee->ptrace = PT_PTRACED;
...
now we are tracing task w/ a sid
that we didn't authorize to trace
What do you think?
thanks,
-chris
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists