From: Oleg Nesterov <oleg@redhat.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: serge@hallyn.com,
syzbot <syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com>,
jmorris@namei.org, keescook@chromium.org,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: KASAN: use-after-free Read in task_is_descendant
Date: Thu, 25 Oct 2018 18:25:54 +0200 [thread overview]
Message-ID: <20181025162554.GG3725@redhat.com> (raw)
In-Reply-To: <20181025155503.GF3725@redhat.com>
On 10/25, Oleg Nesterov wrote:
>
> Because our rcu read-lock critical section extends beyond the return from
> synchronize_rcu(), and thus we must have a full memory barrier _between_
> that synchronize_rcu() and our rcu_read_lock(). We must see all memory updates,
> including thread_pid = NULL which makes pid_alive() == F.
In case I was not clear....
Suppose we have int X = 0. If some CPU does
X = 1;
synchronize_rcu();
and another CPU does
rcu_read_lock();
x = X;
rcu_read_unlock();
then x should be == 1 in case when rcu_read_unlock() happens _after_ return
from synchronize_rcu().
Oleg.
next prev parent reply other threads:[~2018-10-25 16:26 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-21 7:10 KASAN: use-after-free Read in task_is_descendant syzbot
2018-10-21 7:12 ` Tetsuo Handa
2018-10-22 9:54 ` Oleg Nesterov
2018-10-22 10:06 ` Tetsuo Handa
2018-10-22 13:46 ` Oleg Nesterov
2018-10-25 2:15 ` Tetsuo Handa
2018-10-25 11:13 ` Oleg Nesterov
2018-10-25 11:36 ` Kees Cook
2018-10-25 12:05 ` Oleg Nesterov
2018-10-25 11:47 ` Tetsuo Handa
2018-10-25 12:17 ` Oleg Nesterov
2018-10-25 13:01 ` Oleg Nesterov
2018-10-26 16:09 ` Kees Cook
2018-10-29 12:23 ` Oleg Nesterov
2018-10-29 15:05 ` yama: unsafe usage of ptrace_relation->tracer Oleg Nesterov
2019-01-10 11:05 ` Tetsuo Handa
2019-01-10 18:47 ` Kees Cook
2019-01-16 17:40 ` Oleg Nesterov
2018-10-25 13:14 ` KASAN: use-after-free Read in task_is_descendant Tetsuo Handa
2018-10-25 15:55 ` Oleg Nesterov
2018-10-25 16:25 ` Oleg Nesterov [this message]
2018-10-26 12:23 ` Tetsuo Handa
2018-10-26 13:04 ` Oleg Nesterov
2018-10-26 13:51 ` Tetsuo Handa
2018-10-26 14:39 ` Oleg Nesterov
2018-10-26 15:04 ` Tetsuo Handa
2018-10-26 15:22 ` Oleg Nesterov
2018-10-25 8:19 ` Kees Cook
2018-10-25 11:52 ` Oleg Nesterov
2018-11-10 3:25 ` syzbot
2018-11-10 11:46 ` syzbot
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