Re: proc_flush_task oops

From: Eric W. Biederman
Date: Tue Dec 19 2017 - 13:28:01 EST

Dave Jones <davej@xxxxxxxxxxxxxxxxx> writes:

> On Mon, Dec 18, 2017 at 03:50:52PM -0800, Linus Torvalds wrote:
> > But I don't see what would have changed in this area recently.
> >
> > Do you end up saving the seeds that cause crashes? Is this
> > reproducible? (Other than seeing it twoce, of course)
> Only clue so far, is every time I'm able to trigger it, the last thing
> the child process that triggers it did, was an execveat.

Is there any chance the excveat might be called from a child thread?

That switching pids between tasks of a process during exec can get a
little bit tricky.

> Telling it to just fuzz execveat doesn't instantly trigger it, so it
> must be a combination of some other syscall. I'll leave a script running
> overnight to see if I can binary search the other syscalls in
> combination with it.

Could we have a buggy syscall that is stomping something?

> One other thing: I said this was rc4, but it was actually rc4 + all the
> x86 stuff from today. There's enough creepy stuff in that pile, that
> I'll try with just plain rc4 tomorrow too.