linux-kernel - Re: [PATCH 3/3] Add timeout feature

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: <48E0EA0B.7000701@sandeen.net>
Date:	Mon, 29 Sep 2008 09:45:31 -0500
From:	Eric Sandeen <sandeen@...deen.net>
To:	Christoph Hellwig <hch@...radead.org>
CC:	Takashi Sato <t-sato@...jp.nec.com>,
	Ric Wheeler <rwheeler@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...sign.ru>, linux-fsdevel@...r.kernel.org,
	dm-devel@...hat.com, viro@...IV.linux.org.uk,
	linux-ext4@...r.kernel.org, xfs@....sgi.com, axboe@...nel.dk,
	mtk.manpages@...glemail.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] Add timeout feature

Christoph Hellwig wrote:
> On Mon, Sep 29, 2008 at 09:36:04AM -0500, Eric Sandeen wrote:
>> Christoph Hellwig wrote:
>>> On Fri, Sep 26, 2008 at 05:52:35PM +0900, Takashi Sato wrote:
>>>> I think that your concern is that the freezer cannot recognize the occurrence
>>>> of a timeout and it continues the backup process and the backup data is
>>>> corrupted finally.
>>> What timeout should happen?  the freeze ioctl must not return until the
>>> filesystem is a clean state and all writes are blocked.
>> The suggestion was that *UN*freeze would return ETIMEDOUT if the
>> filesystem had already unfrozen itself, I think.  That way you know that
>> the snapshot you just took is worthless, at least.
> 
> But why would the filesystem every unfreeze itself?  That defeats the
> whole point of freezing it.

I agree.  Was just trying to clarify the above point.

But there have been what, 12 submissions now, with the unfreeze timeout
in place so it's a persistent theme ;)

Perhaps a demonstration of just how easy (or not easy) it is to deadlock
a filesystem by freezing the root might be in order, at least.

And even if it is relatively easy, I still maintain that it is the
administrator's role to not inflict damage on the machine being
administered.  There are a lot of potentially dangerous tools at root's
disposal; why this particular one needs a nanny I'm still not quite sure.

-Eric
--
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/