linux-kernel - Re: KASAN: use-after-free Read in task_is

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Message-ID: <20181025130129.GE3725@redhat.com>
Date:   Thu, 25 Oct 2018 15:01:30 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     serge@...lyn.com,
        syzbot <syzbot+a9ac39bf55329e206219@...kaller.appspotmail.com>,
        jmorris@...ei.org, keescook@...omium.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: use-after-free Read in task_is_descendant

On 10/25, Oleg Nesterov wrote:
>
> As I said below, please ignore ptracer_exception_found(), another caller for now,
> perhaps it needs some changes too. I even have a vague feeling that I have already
> blamed this function some time ago...

Heh, yes, 3 years ago ;)

https://lore.kernel.org/lkml/20150106184427.GA18153@redhat.com/

I can't understand my email today, but note that I tried to point out that
task_is_descendant() can dereference the freed mem.

And yes, task_is_descendant() is overcompicated for no reason, afaics.

Oleg.