linux-kernel - Re: /proc/<pid>/maps question....why aren't adjacent memory chunks merged?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Fri, 14 May 2010 14:27:34 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Chris Friesen <cfriesen@...tel.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: /proc/<pid>/maps question....why aren't adjacent memory chunks
 merged?

On Thu, May 13, 2010 at 03:34:04PM -0600, Chris Friesen wrote:
>Hi,
>
>I've got a system running a somewhat-modified 2.6.27 on 64-bit x86.
>
>While investigating a userspace memory leak issue I noticed that
>/proc/<pid>/maps showed a bunch of adjacent anonymous memory chunks with
>identical permissions:
>
>7fd048000000-7fd04c000000 rw-p 00000000 00:00 0
>7fd04c000000-7fd050000000 rw-p 00000000 00:00 0
>7fd050000000-7fd054000000 rw-p 00000000 00:00 0
>7fd054000000-7fd058000000 rw-p 00000000 00:00 0
>7fd058000000-7fd05c000000 rw-p 00000000 00:00 0
>7fd05c000000-7fd060000000 rw-p 00000000 00:00 0
>7fd060000000-7fd064000000 rw-p 00000000 00:00 0
>7fd064000000-7fd068000000 rw-p 00000000 00:00 0
>7fd068000000-7fd06c000000 rw-p 00000000 00:00 0
>7fd06c000000-7fd070000000 rw-p 00000000 00:00 0
>7fd070000000-7fd074000000 rw-p 00000000 00:00 0
>7fd074000000-7fd078000000 rw-p 00000000 00:00 0
>7fd078000000-7fd07c000000 rw-p 00000000 00:00 0
>7fd07c000000-7fd07fffe000 rw-p 00000000 00:00 0
>
>I was under the impression that the kernel would merge areas together in
>this circumstance.  Does anyone have an idea about what's going on here?
>

Well, that is not so simple, there are other considerations,
you need to check vma_merge(), especially can_vma_merge_{after,before}().

Thanks.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/