Re: [PATCH 3/3] bpf: Make sure that ->comm does not change under us.

[Daniel Borkmann]

On 10/16/2017 10:55 PM, Richard Weinberger wrote:
> Am Montag, 16. Oktober 2017, 22:50:43 CEST schrieb Daniel Borkmann:
> > >    	struct task_struct *task = current;
> > >
> > > +	task_lock(task);
> > >
> > >    	strncpy(buf, task->comm, size);
> > >
> > > +	task_unlock(task);
> >
> > Wouldn't this potentially lead to a deadlock? E.g. you attach yourself
> > to task_lock() / spin_lock() / etc, and then the BPF prog triggers the
> > bpf_get_current_comm() taking the lock again ...
>
> Yes, but doesn't the same apply to the use case when I attach to strncpy()
> and run bpf_get_current_comm()?

You mean due to recursion? In that case trace_call_bpf() would bail out
due to the bpf_prog_active counter.