All of lore.kernel.org
 help / color / mirror / Atom feed
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


_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=52312047.2010701@jp.fujitsu.com \
    --to=d.hatayama@jp.fujitsu.com \
    --cc=kexec@lists.infradead.org \
    --cc=kumagai-atsushi@mxc.nes.nec.co.jp \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.