linux-kernel - Re: [PATCH] mm: hwpoison: fix thp split handing in soft_offline_in_use

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

Message-ID: <20190226135156.mifspmbdyr6m3hff@kshutemo-mobl1>
Date:   Tue, 26 Feb 2019 16:51:56 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     zhong jiang <zhongjiang@...wei.com>
Cc:     n-horiguchi@...jp.nec.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org, mhocko@...e.com,
        hughd@...gle.com, mhocko@...nel.org
Subject: Re: [PATCH] mm: hwpoison: fix thp split handing in
 soft_offline_in_use_page()

On Tue, Feb 26, 2019 at 07:18:00PM +0800, zhong jiang wrote:
> From: zhongjiang <zhongjiang@...wei.com>
> 
> When soft_offline_in_use_page() runs on a thp tail page after pmd is plit,

s/plit/split/

> we trigger the following VM_BUG_ON_PAGE():
> 
> Memory failure: 0x3755ff: non anonymous thp
> __get_any_page: 0x3755ff: unknown zero refcount page type 2fffff80000000
> Soft offlining pfn 0x34d805 at process virtual address 0x20fff000
> page:ffffea000d360140 count:0 mapcount:0 mapping:0000000000000000 index:0x1
> flags: 0x2fffff80000000()
> raw: 002fffff80000000 ffffea000d360108 ffffea000d360188 0000000000000000
> raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
> ------------[ cut here ]------------
> kernel BUG at ./include/linux/mm.h:519!
> 
> soft_offline_in_use_page() passed refcount and page lock from tail page to
> head page, which is not needed because we can pass any subpage to
> split_huge_page().

I don't see a description of what is going wrong and why change will fixed
it. From the description, it appears as it's cosmetic-only change.

Please elaborate.

-- 
 Kirill A. Shutemov