From: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
To: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: kexec@lists.infradead.org
Subject: Re: [PATCH v2 10/10] Warn cyclic buffer overrun and correct it if possible
Date: Thu, 12 Sep 2013 11:00:39 +0900 [thread overview]
Message-ID: <52312047.2010701@jp.fujitsu.com> (raw)
In-Reply-To: <52302B6D.8060103@jp.fujitsu.com>
(2013/09/11 17:35), HATAYAMA Daisuke wrote:
> (2013/09/11 16:51), Atsushi Kumagai wrote:
>> Hello HATAYAMA-san,
>>
>> (2012/11/16 14:02), HATAYAMA Daisuke wrote:
>>> Clearling bits on cyclic buffer can overrun the cyclic buffer
>>> according to some combination of MAX_ORDER and cyclic buffer size.
>>>
>>> The cyclic buffer size is corrected if possible.
>>>
>>> Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
>>
>> I know it's so late, I found that updating pfn_cyclic is missing.
>> It can cause memory corruption.
>>
>
> Hello Kumagai-san,
>
> Reviewed-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
>
> It might be even better to introduce some kind of helper function that
> sets up these cyclic-mode-related parameters and then to use it in
> initial() and check_cyclic_buffer_overrun().
>
Hello Kumaga-san,
I found one more bug. Could you review it?
From c98375b9af6c19dff88823166eaf13674b4a47ec Mon Sep 17 00:00:00 2001
From: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Date: Thu, 12 Sep 2013 10:35:17 +0900
Subject: [PATCH] Use divideup() to calculate maximum required bitmap size
Currently, check_cyclic_buffer_overrun() wrongly calculates maximum
bitmap size required to represent maximum block size managed by buddy
allocator with roundup(). Then, max_block_size is BITPERBYTE-time
larger than its correct size. As a result, although the bug never
affect free-page filtering since roundup(max_order_nr_pages,
BITPERBYTE) is a multiple of divideup(max_order_nr_pages, BITPERBYTE),
the following sanity check, (max_block_size > info->bufsize_cyclic),
and recalculation of info->bufsize_cyclic becomes BITPERBYTE-time
conservative and inefficient.
Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
---
makedumpfile.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/makedumpfile.c b/makedumpfile.c
index 164b3f1..e66c494 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -4078,10 +4078,10 @@ check_cyclic_buffer_overrun(void)
{
int max_order = ARRAY_LENGTH(zone.free_area);
int max_order_nr_pages = 1 << (max_order - 1);
- unsigned long max_block_size = roundup(max_order_nr_pages, BITPERBYTE);
+ unsigned long max_block_size = divideup(max_order_nr_pages,
+ BITPERBYTE);
- if (info->bufsize_cyclic %
- roundup(max_order_nr_pages, BITPERBYTE)) {
+ if (info->bufsize_cyclic % max_block_size) {
unsigned long bufsize;
if (max_block_size > info->bufsize_cyclic) {
--
1.8.3.1
--
Thanks.
HATAYAMA, Daisuke
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next prev parent reply other threads:[~2013-09-12 2:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-16 5:01 [PATCH v2 00/10] Support free page filtering looking up mem_map array HATAYAMA Daisuke
2012-11-16 5:01 ` [PATCH v2 01/10] Move page flags setup for old kernels after debuginfo initialization HATAYAMA Daisuke
2012-11-16 5:01 ` [PATCH v2 02/10] Add debuginfo interface for enum type size HATAYAMA Daisuke
2012-11-16 5:01 ` [PATCH v2 03/10] Add new parameters to various tables HATAYAMA Daisuke
2012-11-16 5:01 ` [PATCH v2 04/10] Add debuginfo-related processing for VMCOREINFO/VMLINUX HATAYAMA Daisuke
2012-11-16 5:01 ` [PATCH v2 05/10] Add hardcoded page flag values HATAYAMA Daisuke
2012-11-16 5:02 ` [PATCH v2 06/10] Exclude free pages by looking up mem_map array HATAYAMA Daisuke
2012-11-16 5:02 ` [PATCH v2 07/10] Add page_is_buddy for recent kernels HATAYAMA Daisuke
2012-11-16 5:02 ` [PATCH v2 08/10] Add page_is_buddy for PG_buddy HATAYAMA Daisuke
2012-11-27 6:00 ` Atsushi Kumagai
2012-11-27 7:30 ` Atsushi Kumagai
2012-11-27 8:53 ` Hatayama, Daisuke
2012-11-28 7:42 ` Atsushi Kumagai
2012-11-16 5:02 ` [PATCH v2 09/10] Add page_is_buddy for old kernels HATAYAMA Daisuke
2012-11-16 5:02 ` [PATCH v2 10/10] Warn cyclic buffer overrun and correct it if possible HATAYAMA Daisuke
2013-09-11 7:51 ` Atsushi Kumagai
2013-09-11 8:35 ` HATAYAMA Daisuke
2013-09-12 2:00 ` HATAYAMA Daisuke [this message]
2013-09-12 6:17 ` Atsushi Kumagai
2012-11-16 7:05 ` [PATCH v2 00/10] Support free page filtering looking up mem_map array Atsushi Kumagai
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