linux-kernel - Re: VM: Fix nasty and subtle race in shared mmap'ed page writeback

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: <20070103230629.a2e734b9.akpm@osdl.org>
Date:	Wed, 3 Jan 2007 23:06:29 -0800
From:	Andrew Morton <akpm@...l.org>
To:	David Miller <davem@...emloft.net>
Cc:	nickpiggin@...oo.com.au, torvalds@...l.org, gelma@...ma.net,
	linux-kernel@...r.kernel.org
Subject: Re: VM: Fix nasty and subtle race in shared mmap'ed page writeback

On Wed, 03 Jan 2007 22:56:07 -0800 (PST)
David Miller <davem@...emloft.net> wrote:

> From: Andrew Morton <akpm@...l.org>
> Date: Wed, 3 Jan 2007 22:12:20 -0800
> 
> > On Thu, 04 Jan 2007 17:03:43 +1100
> > Nick Piggin <nickpiggin@...oo.com.au> wrote:
> > 
> > > > That bug was introduced in 2.6.19, with the dirty page tracking patches.
> > > > 
> > > > 2.6.18 and earlier used ->private_lock coverage in try_to_free_buffers() to
> > > > prevent it.
> > > 
> > > Ohh, right you are, I was looking at 2.6.19 sources. The comments above
> > > ttfb match that as well. Curious that the dirty page patches were allowed
> > > to mess with this...
> > 
> > Frankly, those patches scared the crap out of me, specifically because of
> > the delicacy and complexity of the various dirtiness state coherencies. 
> > But I just didn't have the bandwidth to go through them with a sufficiently
> > fine toothcomb, sorry.
> > 
> > > Anyway that leaves us with the question of why Andrea's database is getting
> > > corrupted. Hopefully he can give us a minimal test-case.
> > 
> > It'd odd that stories of pre-2.6.19 BerkeleyDB corruption are now coming
> > out of the woodwork.  It's the first I've ever heard of them.
> 
> Note that the original rtorrent debian bug report was against 2.6.18

I think that was 2.6.18+debian-added-dirty-page-tracking-patches.

If that memory is correct, I'll assert (and emphasise) that the cause of the
alleged BerkeleyDB corruption is not known at this time.

The post-2.6.19 "fix" might make it go away.  But if it does, we do not know
why, and it might still be there, only harder to hit.

-
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/