From: David Howells <dhowells@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: dhowells@redhat.com, "Serge E. Hallyn" <serge@hallyn.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
"Serge E. Hallyn" <serge.hallyn@canonical.com>,
lkml <linux-kernel@vger.kernel.org>,
richard@nod.at, "Eric W. Biederman" <ebiederm@xmission.com>,
Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check
Date: Tue, 20 Sep 2011 17:27:30 +0100 [thread overview]
Message-ID: <5425.1316536050@redhat.com> (raw)
In-Reply-To: <20110920143942.GB15859@redhat.com>
Oleg Nesterov <oleg@redhat.com> wrote:
> From 8f92054e commit:
>
> Instead, add the following validation condition:
>
> task->exit_state >= 0
>
> to permit the access if the target task is dead and therefore unable to change
> its own credentials.
>
> OK, but afaics currently this can only help wait_task_zombie() which
> calls __task_cred() without rcu lock.
>
> Remove this validation and change wait_task_zombie() to use task_uid()
> instead. This means we do rcu_read_lock() only to shut up the lockdep,
> but we already do the same in, say, wait_task_stopped().
>
> Unfortunately, we can't kill task_is_dead() right now, it has already
> found the users in drivers/staging/, and I bet the usage is wrong.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
It simplifies stuff in exchange for the most minor of slowdowns, so fair
enough.
next prev parent reply other threads:[~2011-09-20 16:28 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-19 21:45 [PATCH] user namespace: make signal.c respect user namespaces Serge E. Hallyn
2011-09-19 21:47 ` [PATCH] user namespace: usb: make usb urbs user namespace aware Serge E. Hallyn
2011-09-20 13:17 ` Oleg Nesterov
2011-09-20 13:33 ` Serge E. Hallyn
2011-09-21 5:01 ` [PATCH] user namespace: usb: make usb urbs user namespace aware (v2) Serge E. Hallyn
2011-09-21 18:31 ` Oleg Nesterov
2011-09-21 19:12 ` Serge E. Hallyn
2011-09-21 19:18 ` Greg KH
2011-09-23 1:27 ` [PATCH resend] " Serge E. Hallyn
2011-09-23 15:48 ` Alan Stern
2011-09-23 16:06 ` Serge E. Hallyn
2011-09-23 16:21 ` Alan Stern
2011-09-23 17:22 ` Serge E. Hallyn
2011-09-23 18:35 ` Alan Stern
2011-09-20 12:22 ` [PATCH] user namespace: make signal.c respect user namespaces Oleg Nesterov
2011-09-20 12:44 ` Serge E. Hallyn
2011-09-20 13:41 ` Oleg Nesterov
2011-09-20 14:39 ` [PATCH 0/2] (Was: user namespace: make signal.c respect user namespaces) Oleg Nesterov
2011-09-20 14:39 ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check Oleg Nesterov
2011-09-20 15:14 ` drivers/staging/usbip/ abuses task_is_dead/exit_state Oleg Nesterov
2011-09-20 18:38 ` Greg KH
2012-03-06 17:39 ` ping: " Oleg Nesterov
2012-03-06 19:30 ` Tobias Klauser
2012-03-08 18:57 ` Oleg Nesterov
2012-03-13 11:45 ` Tobias Klauser
2012-03-13 18:07 ` [PATCH] staging: usbip: fix the usage of kthread_stop() Oleg Nesterov
2012-04-01 23:17 ` Oleg Nesterov
2012-04-02 8:11 ` Tobias Klauser
2011-09-20 15:28 ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check Paul E. McKenney
2011-09-20 15:40 ` Oleg Nesterov
2011-09-20 15:48 ` Paul E. McKenney
2011-09-20 16:27 ` David Howells [this message]
2011-09-20 14:39 ` [PATCH 2/2] creds: __task_cred(current) doesn't need rcu_read_lock_held() Oleg Nesterov
2011-09-20 15:07 ` Serge Hallyn
2011-09-20 15:35 ` Oleg Nesterov
2011-09-20 16:19 ` David Howells
2011-09-20 16:38 ` Oleg Nesterov
2011-09-20 16:50 ` David Howells
2011-09-20 17:13 ` Oleg Nesterov
2011-09-20 15:39 ` [PATCH] user namespace: make signal.c respect user namespaces Serge Hallyn
2011-09-20 16:24 ` Oleg Nesterov
2011-09-20 16:45 ` Serge E. Hallyn
2011-09-20 18:17 ` Oleg Nesterov
2011-09-21 5:00 ` [PATCH] user namespace: make signal.c respect user namespaces (v2) Serge E. Hallyn
2011-09-20 17:48 ` [PATCH] user namespace: make signal.c respect user namespaces Oleg Nesterov
2011-09-20 18:53 ` Serge E. Hallyn
2011-09-21 17:53 ` Oleg Nesterov
2011-09-22 15:23 ` Serge Hallyn
2011-09-23 16:31 ` Serge E. Hallyn
2011-09-23 17:36 ` Oleg Nesterov
2011-09-23 21:20 ` Serge E. Hallyn
2011-09-24 16:37 ` Oleg Nesterov
2011-09-25 20:17 ` Serge E. Hallyn
2011-09-26 16:06 ` Oleg Nesterov
2011-09-27 14:28 ` Serge Hallyn
2011-09-27 14:38 ` Oleg Nesterov
2011-09-27 15:27 ` Serge Hallyn
2011-09-27 17:12 ` Oleg Nesterov
2011-10-04 17:42 ` Serge E. Hallyn
2011-10-09 19:00 ` Oleg Nesterov
2011-10-11 13:08 ` Serge E. Hallyn
2011-10-08 20:02 ` Serge E. Hallyn
2011-10-09 19:03 ` Oleg Nesterov
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