Am Montag, 16. Oktober 2017, 23:02:06 CEST schrieb 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.
Ah, that's true. So, when someone wants to use bpf_get_current_comm() while tracing task_lock, we have a problem. I agree. On the other hand, without locking the function may return wrong results. Thanks, //richard
