linux-kernel - Re: bad page state in 3.13-rc4

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: <20131219195352.GB9228@kvack.org>
Date:	Thu, 19 Dec 2013 14:53:52 -0500
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Kent Overstreet <kmo@...erainc.com>, Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, Christoph Lameter <cl@...two.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: bad page state in 3.13-rc4

On Fri, Dec 20, 2013 at 04:45:38AM +0900, Linus Torvalds wrote:
> On Fri, Dec 20, 2013 at 4:26 AM, Benjamin LaHaise <bcrl@...ck.org> wrote:
> >
> > Okay, I'll rewriting it to use truncate to free the pages.
> 
> It already does that in put_aio_ring_file() afaik. No?

Yes, that's what I found when I started looking into this in detail again.  
I think the page reference counting is actually correct.  There are 2 
references on each page: the first is from the find_or_create_page() call, 
and the second is from the get_user_pages() (which also makes sure the page 
is populated into the page tables).  The only place I can see things going 
off the rails is if the get_user_pages() call fails.  It's possible trinity 
could be arranging things so that the get_user_pages() call is failing 
somehow.  Also, if it were a double free of a page, we should at least get 
a VM_BUG() occuring when the page's count is 0.

Dave -- do you have CONFIG_DEBUG_VM on in your test rig?

>                 Linus

-- 
"Thought is the essence of where you are now."
--
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/