From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: john.stultz@linaro.org
Cc: linux-kernel@vger.kernel.org, tytso@mit.edu, rientjes@google.com,
dave@linux.vnet.ibm.com, akpm@linux-foundation.org,
linux-mm@kvack.org
Subject: Re: [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access
Date: Wed, 18 May 2011 09:28:36 +0900 [thread overview]
Message-ID: <4DD312B4.7060008@jp.fujitsu.com> (raw)
In-Reply-To: <1305580757-13175-2-git-send-email-john.stultz@linaro.org>
(2011/05/17 6:19), John Stultz wrote:
> The implicit rules for current->comm access being safe without locking
> are no longer true. Accessing current->comm without holding the task
> lock may result in null or incomplete strings (however, access won't
> run off the end of the string).
>
> In order to properly fix this, I've introduced a comm_lock spinlock
> which will protect comm access and modified get_task_comm() and
> set_task_comm() to use it.
>
> Since there are a number of cases where comm access is open-coded
> safely grabbing the task_lock(), we preserve the task locking in
> set_task_comm, so those users are also safe.
>
> With this patch, users that access current->comm without a lock
> are still prone to null/incomplete comm strings, but it should
> be no worse then it is now.
>
> The next step is to go through and convert all comm accesses to
> use get_task_comm(). This is substantial, but can be done bit by
> bit, reducing the race windows with each patch.
>
> CC: Ted Ts'o<tytso@mit.edu>
> CC: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>
> CC: David Rientjes<rientjes@google.com>
> CC: Dave Hansen<dave@linux.vnet.ibm.com>
> CC: Andrew Morton<akpm@linux-foundation.org>
> CC: linux-mm@kvack.org
> Acked-by: David Rientjes<rientjes@google.com>
> Signed-off-by: John Stultz<john.stultz@linaro.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
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next prev parent reply other threads:[~2011-05-18 0:28 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-16 21:19 [PATCH 0/3] v4 Improve task->comm locking situation John Stultz
2011-05-16 21:19 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-05-16 22:01 ` Jiri Slaby
2011-05-17 1:47 ` John Stultz
2011-05-18 0:28 ` KOSAKI Motohiro [this message]
2011-05-16 21:19 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-16 21:54 ` Jiri Slaby
2011-05-16 23:10 ` John Stultz
2011-05-16 23:56 ` Joe Perches
2011-05-17 0:11 ` John Stultz
2011-05-17 7:21 ` Jiri Slaby
2011-05-18 0:32 ` KOSAKI Motohiro
2011-05-16 21:19 ` [PATCH 3/3] checkpatch.pl: Add check for task comm references John Stultz
2011-05-16 21:29 ` Michal Nazarewicz
2011-05-16 21:34 ` David Rientjes
2011-05-16 23:04 ` Joe Perches
2011-05-16 23:11 ` Michal Nazarewicz
2011-05-16 23:22 ` Joe Perches
-- strict thread matches above, loose matches on Subject: below --
2011-05-12 23:02 [PATCH 0/3] v3 Improve task->comm locking situation John Stultz
2011-05-12 23:02 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-05-13 11:13 ` KOSAKI Motohiro
2011-05-13 18:27 ` John Stultz
2011-05-14 11:12 ` KOSAKI Motohiro
2011-05-16 20:34 ` John Stultz
2011-05-11 0:23 [RFC][PATCH 0/3] v2 Improve task->comm locking situation John Stultz
2011-05-11 0:23 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-05-11 17:39 ` Andi Kleen
2011-05-12 22:00 ` David Rientjes
2011-04-28 4:03 [RFC][PATCH 0/3] Improve task->comm locking situation John Stultz
2011-04-28 4:03 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
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