From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: John Stultz <john.stultz@linaro.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Ted Ts'o <tytso@mit.edu>,
David Rientjes <rientjes@google.com>,
Dave Hansen <dave@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access
Date: Sat, 14 May 2011 20:12:10 +0900 [thread overview]
Message-ID: <BANLkTin_MitzRUkWToj055AuAPdMC9msXQ@mail.gmail.com> (raw)
In-Reply-To: <1305311276.2680.34.camel@work-vm>
>> Can you please explain why we should use seqlock? That said,
>> we didn't use seqlock for /proc items. because, plenty seqlock
>> write may makes readers busy wait. Then, if we don't have another
>> protection, we give the local DoS attack way to attackers.
>
> So you're saying that heavy write contention can cause reader
> starvation?
Yes.
>> task->comm is used for very fundamentally. then, I doubt we can
>> assume write is enough rare. Why can't we use normal spinlock?
>
> I think writes are likely to be fairly rare. Tasks can only name
> themselves or sibling threads, so I'm not sure I see the risk here.
reader starvation may cause another task's starvation if reader have
an another lock.
And, "only sibling" don't make any security gurantee as I said past.
Thanks.
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next prev parent reply other threads:[~2011-05-14 11:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
2011-05-16 20:34 ` John Stultz
2011-05-12 23:02 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-12 23:02 ` [PATCH 3/3] checkpatch.pl: Add check for current->comm references John Stultz
2011-05-13 6:33 ` Jiri Slaby
2011-05-13 11:02 ` Michal Nazarewicz
2011-05-16 21:23 ` David Rientjes
2011-05-13 11:13 ` KOSAKI Motohiro
2011-05-13 18:28 ` John Stultz
-- strict thread matches above, loose matches on Subject: below --
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
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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