Re: ptrace patch fails stress testing

[Alan Cox]

On Tue, 2003-04-01 at 19:22, [e-mail] wrote:
> The problem appears to be that task->mm is dereferenced without 
> looking to see if mm is NULL.  e.g. in the sched.h in the 
> is_dumpable() macro, we have task->mm->dumpable .  I'm sitting
> in front of a KDB session and I'm clearly looking at task->mm
> which is NULL. 
> Why, how and under what conditions this race condition occurs, 
> I don't know.  What the best fix is, I don't know.

Zombie process. The patch checks ->mm but must also check ->mm != NULL
first.

> I can try to just add a check for NULL, but I'd like someone 
> to tell me that 'yes this is the right way to fix this.' 

It is I think.

Alan