Messages in this thread | | | Date | Fri, 26 Oct 2018 16:39:37 +0200 | From | Oleg Nesterov <> | Subject | Re: KASAN: use-after-free Read in task_is_descendant |
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On 10/26, Tetsuo Handa wrote: > > On 2018/10/26 22:04, Oleg Nesterov wrote: > >> Suppose p1 == p2->real_parent and p2 == p3->real_parent, and p1 exited > >> when p2 tried to attach on p1, p2->real_parent was pointing to already > >> (or about to be) freed p1. > > > > No, p2->real_parent will be updated. If p1 exits it will re-parent its > > children including p2. > > My error. > > Suppose p1 == p2->real_parent and p2 == p3->real_parent, and p1 exited > when someone tried to attach on p2, p2->real_parent was pointing to already > (or about to be) freed p1.
I don't see a difference.
If p1 exits it will re-parent p2, p2->real_parent will be updated.
> So, the puzzle part is why p2->real_parent was still pointing p1 even after > p1 was freed...
I don't understand the question.
Once again. TASK->real_parent can point to the freed mem only if a) TASK exits, and b) _after_ that its parent TASK->real_parent exits too.
> > Again, did you read my previous email? > > Yes. But I still can't be convinced that pid_alive() test helps.
Well, I don't understand which part of my explanations is not clear to you.
OR. Perhaps I am wrong and do not understand your concerns.
Oleg.
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