From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: David Rientjes <rientjes@google.com>
Cc: Ryota Ozaki <ozaki.ryota@gmail.com>,
linux-kernel@vger.kernel.org, Greg Kroah-Hartman <gregkh@suse.de>,
linux-mm@kvack.org, stable@kernel.org
Subject: Re: [PATCH][RESEND] mm: Fix off-by-one bug in print_nodes_state
Date: Sun, 18 Dec 2011 17:48:32 -0500 [thread overview]
Message-ID: <4EEE6DC0.2030007@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1112181439500.1364@chino.kir.corp.google.com>
(12/18/11 5:44 PM), David Rientjes wrote:
> On Sun, 18 Dec 2011, Ryota Ozaki wrote:
>
>> /sys/devices/system/node/{online,possible} involve a garbage byte
>> because print_nodes_state returns content size + 1. To fix the bug,
>> the patch changes the use of cpuset_sprintf_cpulist to follow the
>> use at other places, which is clearer and safer.
>>
>
> It's not a garbage byte, sysdev files use a buffer created with
> get_zeroed_page(), so extra byte is guaranteed to be zero since
> nodelist_scnprintf() won't write to it. So the issue here is that
> print_nodes_state() returns a size that is off by one according to
> ISO C99 although it won't cause a problem in practice.
>
>> This bug was introduced since v2.6.24.
>>
>
> It's not a bug, the result of a 4-node system would be "0-3\n\0" and
> returns 5 correctly. You can verify this very simply with strace.
Usually, /sys files don't output trailing 'JPY0'. And, 'JPY0' is not regular
io friendly. So I can imagine some careless programmer think it is
garbage. Is there any benefit to show trailing 'JPY0'?
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next prev parent reply other threads:[~2011-12-18 22:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-18 11:58 [PATCH][RESEND] mm: Fix off-by-one bug in print_nodes_state Ryota Ozaki
2011-12-18 21:28 ` KOSAKI Motohiro
2011-12-20 4:22 ` Ryota Ozaki
2011-12-18 22:44 ` David Rientjes
2011-12-18 22:48 ` KOSAKI Motohiro [this message]
2011-12-19 20:53 ` David Rientjes
2011-12-19 21:15 ` KOSAKI Motohiro
2011-12-20 4:43 ` Ryota Ozaki
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