linux-kernel - Re: [PATCH] mm/memory-failure: fix race with compound page split/merge

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:	Thu, 21 Apr 2016 16:44:54 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH] mm/memory-failure: fix race with compound page
 split/merge

On Mon, 18 Apr 2016 23:15:52 +0000 Naoya Horiguchi <n-horiguchi@...jp.nec.com> wrote:

> # CCed Andrew,

Thanks.

> On Mon, Apr 18, 2016 at 02:43:45PM +0300, Konstantin Khlebnikov wrote:
> > Get_hwpoison_page() must recheck relation between head and tail pages.
> > 
> > Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> 
> Looks good to me. Without this recheck, the race causes kernel to pin
> an irrelevant page, and finally makes kernel crash for refcount mismcach...

Thanks.  I'll add the above (important!) info to the changelog and
cc:stable.

> > -	return get_page_unless_zero(head);
> > +	if (get_page_unless_zero(head)) {
> > +		if (head == compound_head(page))
> > +			return 1;
> > +
> > +		pr_info("MCE: %#lx cannot catch tail\n", page_to_pfn(page));
> 
> Recently Chen Yucong replaced the label "MCE:" with "Memory failure:",
> but the resolution is trivial, I think.

Yup, that patch is in my (large) backlog.  Away at conferences for
seven days, receiving 100 actionable emails per day.  Give me a few
days ;)