linux-kernel - Re: 2.6.19 file content corruption on ext3

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: <Pine.LNX.4.64.0612171716510.3479@woody.osdl.org>
Date:	Sun, 17 Dec 2006 17:22:57 -0800 (PST)
From:	Linus Torvalds <torvalds@...l.org>
To:	Andrew Morton <akpm@...l.org>
cc:	andrei.popa@...eo.ro,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hugh Dickins <hugh@...itas.com>,
	Florian Weimer <fw@...eb.enyo.de>,
	Marc Haber <mh+linux-kernel@...schlus.de>,
	Martin Michlmayr <tbm@...ius.com>
Subject: Re: 2.6.19 file content corruption on ext3

On Sun, 17 Dec 2006, Andrew Morton wrote:
> 
> From my quick reading, all callers of try_to_free_buffers() have already
> unmapped the page from pagetables, and given that the reported ext3 corruption
> happens on uniprocessor, non-preempt kernels, I doubt if this patch will fix
> things.

Hmm. One possible explanation: maybe the page actually _did_ get unmapped 
from the page tables, but got added back?

I don't think we lock the page when faulting it in (we want it to be 
uptodate, but not necessarily locked). So assuming the pageout sequence 
always _does_ follow the rule that it only does try_to_free_buffers() on 
pages that aren't mapped, what actually protects them from not becoming 
mapped (and dirtied) during that sequence?

So we should probably do a "wait_for_page()" in do_no_page()?

Or maybe only do it for write accesses (since we don't really care about 
getting mapped readably)? If so, we need to do it in the write case of 
do_no_page() _and_ in the do_wp_page() case. Hmm?

		Linus
-
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/