Re: [PATCH v2 2.6.38-rc8-tip 7/20] 7: uprobes: store/restore original instruction.

Srikar Dronamraju
2011-03-15T09:29:10Z

* Stephen Wilson <wilsons@start.ca> [2011-03-14 14:09:14]:

> On Mon, Mar 14, 2011 at 07:05:22PM +0530, Srikar Dronamraju wrote:
> > static int install_uprobe(struct mm_struct *mm, struct uprobe *uprobe)
> > {
> > - int ret = 0;
> > + struct task_struct *tsk;
> > + int ret = -EINVAL;
> >
> > - /*TODO: install breakpoint */
> > - if (!ret)
> > + get_task_struct(mm->owner);
> > + tsk = mm->owner;
> > + if (!tsk)
> > + return ret;
>
> I think you need to check that tsk != NULL before calling
> get_task_struct()...
>

Guess checking for tsk != NULL would only help if and only if we are doing
within rcu. i.e we have to change to something like this

rcu_read_lock()
if (mm->owner) {
get_task_struct(mm->owner)
tsk = mm->owner;
}
rcu_read_unlock()
if (!tsk)
return ret;

Agree?