Messages in this thread | | | Date | Wed, 21 Oct 2009 19:00:28 -0700 | From | Andrew Morton <> | Subject | Re: [RFC][PATCH] Add prctl to set sibling thread names |
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On Wed, 21 Oct 2009 17:52:24 -0700 john stultz <johnstul@us.ibm.com> wrote:
> On Wed, 2009-10-21 at 17:48 -0700, Arjan van de Ven wrote: > > On Wed, 21 Oct 2009 16:21:37 -0700 > > john stultz <johnstul@us.ibm.com> wrote: > > > > > > > > Taking a very raw attempt at this, I scratched out the following > > > simple implementation. I'd appreciate any review or suggestions for > > > improvements. I'm not at all certain the passing of the thread pid_t > > > through the unsigned long is valid, for instance, or if > > > same_thread_group() is the right check to make sure we only change > > > siblings and not tid from other processes. So any advice on better > > > approaches would be great. > > > > > > + return -EINVAL; > > > + > > > + set_task_comm(tsk, comm); > > > > > > you're pretty much the first now who touches ->comm from > > not-the-thread-itself.... are you sure that is safe? > > No, I'm not sure at all :) > > Thanks for pointing this out. I'll see whats needed in set_task_comm(). >
set_task_comm() is OK. The problem will be the unwritten rule that processes can read *their own* ->comm without task_lock(), because nobody ever alters ->comm apart from tack which owns it.
You've changed that, so all the open-coded accesses to current->comm are now racy.
Also, you appear to be running set_task_comm() against a task_struct without holding a reference on that task. Will a well-timed exit() cause a modify-after-free?
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