From: ebiederm@xmission.com (Eric W. Biederman)
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, containers@lists.osdl.org
Subject: Re: [PATCH 5/7] pid: Implement pid_nr
Date: Wed, 16 Aug 2006 10:18:20 -0600 [thread overview]
Message-ID: <m1lkpo3b8z.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <20060816181950.GA472@oleg> (Oleg Nesterov's message of "Wed, 16 Aug 2006 22:19:50 +0400")
Oleg Nesterov <oleg@tv-sign.ru> writes:
> On 08/15, Eric W. Biederman wrote:
>>
>> +static inline pid_t pid_nr(struct pid *pid)
>> +{
>> + pid_t nr = 0;
>> + if (pid)
>> + nr = pid->nr;
>> + return nr;
>> +}
>
> I think this is not safe, you need rcu locks here or the caller should
> do some locking.
>
> Let's look at f_getown() (PATCH 7/7). What if original task which was
> pointed by ->f_owner.pid has gone, another thread does fcntl(F_SETOWN),
> and pid_nr() takes a preemtion after 'if (pid)'? In this case 'pid->nr'
> may follow a freed memory.
This isn't an rcu reference. I hold a hard reference count on
the pid entry. So this should be safe.
What is an rcu reference is going from struct pid to the task
it points to.
Eric
next prev parent reply other threads:[~2006-08-16 16:18 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-15 18:21 Start using struct pid Eric W. Biederman
2006-08-15 18:23 ` [PATCH 1/7] pid: Implement access helpers for a tacks various process groups Eric W. Biederman
2006-08-15 18:40 ` Dave Hansen
2006-08-15 19:03 ` Eric W. Biederman
2006-08-16 8:04 ` [Containers] " Kirill Korotaev
2006-08-15 18:23 ` [PATCH 2/7] pid: Add do_each_pid_task Eric W. Biederman
2006-08-16 3:10 ` [Containers] " Serge E. Hallyn
2006-08-16 4:28 ` Andrew Morton
2006-08-16 6:15 ` Eric W. Biederman
2006-08-16 6:34 ` Eric W. Biederman
2006-08-16 11:57 ` Serge E. Hallyn
2006-08-16 19:17 ` Oleg Nesterov
2006-08-17 21:16 ` [PATCH -mm] simplify pid iterators Oleg Nesterov
2006-08-15 18:23 ` [PATCH 3/7] pid: Implement signal functions that take a struct pid * Eric W. Biederman
2006-08-15 18:23 ` [PATCH 4/7] pid: Export the symbols needed to use " Eric W. Biederman
2006-08-15 18:23 ` [PATCH 5/7] pid: Implement pid_nr Eric W. Biederman
2006-08-15 18:37 ` Dave Hansen
2006-08-15 19:00 ` Eric W. Biederman
2006-08-15 19:15 ` [Containers] " Dave Hansen
2006-08-16 6:29 ` Eric W. Biederman
2006-08-16 16:27 ` Jan Engelhardt
2006-08-16 17:48 ` Eric W. Biederman
2006-08-16 18:19 ` Oleg Nesterov
2006-08-16 16:18 ` Eric W. Biederman [this message]
2006-08-16 21:03 ` Oleg Nesterov
2006-08-16 17:18 ` Eric W. Biederman
2006-08-15 18:23 ` [PATCH 6/7] vt: Update spawnpid to be a struct pid_t Eric W. Biederman
2006-08-15 18:53 ` Alan Cox
2006-08-15 18:45 ` Eric W. Biederman
2006-08-16 8:04 ` [Containers] " Kirill Korotaev
2006-08-16 14:23 ` Eric W. Biederman
2006-08-15 19:38 ` Ray Lehtiniemi
2006-08-16 19:35 ` Oleg Nesterov
2006-08-16 15:43 ` Andrew Morton
2006-08-16 17:55 ` Eric W. Biederman
2006-08-15 18:23 ` [PATCH 7/7] file: Modify struct fown_struct to use a struct pid Eric W. Biederman
2006-08-16 18:45 ` Oleg Nesterov
2006-08-16 18:48 ` Oleg Nesterov
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