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 for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20131224074546.GB27156@lge.com>
Date:	Tue, 24 Dec 2013 16:45:46 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, khlebnikov@...nvz.org,
	LKML <linux-kernel@...r.kernel.org>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Bob Liu <bob.liu@...cle.com>
Subject: Re: mm: kernel BUG at include/linux/swapops.h:131!

On Tue, Dec 24, 2013 at 03:07:05PM +0900, Joonsoo Kim wrote:
> On Mon, Dec 23, 2013 at 10:01:10PM -0500, Sasha Levin wrote:
> > On 12/23/2013 09:51 PM, Joonsoo Kim wrote:
> > >On Mon, Dec 23, 2013 at 12:24:02PM -0500, Sasha Levin wrote:
> > >>>Ping?
> > >>>
> > >>>I've also Cc'ed the "this page shouldn't be locked at all" team.
> > >Hello,
> > >
> > >I can't find the reason of this problem.
> > >If it is reproducible, how about bisecting?
> > 
> > While it reproduces under fuzzing it's pretty hard to bisect it with
> > the amount of issues uncovered by trinity recently.
> > 
> > I can add any debug code to the site of the BUG if that helps.
> 
> Good!
> It will be helpful to add dump_page() in migration_entry_to_page().
> 
> Thanks.
> 

Minchan teaches me that there is possible race condition between
fork and migration.

Please consider following situation.


Process A (do migration)			Process B (parents) Process C (child)

try_to_unmap() for migration <begin>		fork
setup migration entry to B's vma
...
try_to_unmap() for migration <end>
move_to_new_page()

						link new vma
						    into interval tree
remove_migration_ptes() <begin>
check and clear migration entry on C's vma
...						copy_one_pte:
...						    now, B and C have migration entry
...
...
check and clear migration entry on B's vma
...
...
remove_migration_ptes() <end>


Eventually, migration entry on C's vma is left.
And then, when C exits, above BUG_ON() can be triggered.

I'm not sure the I am right, so please think of it together. :)
And I'm not sure again that above assumption is related to this trigger report,
since this may exist for a long time.

So my question to mm folks is is above assumption possible and do we have
any protection mechanism on this race?

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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ