linux-kernel - Re: IMA: kernel reading files opened with O

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: <CACE9dm-NZqC_qz8ip-9wUamwK7daOnKs_dTKQrT+zG4E2BJ=Jw@mail.gmail.com>
Date:	Wed, 2 Jul 2014 22:07:38 +0300
From:	Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	Christoph Hellwig <hch@...radead.org>,
	Dmitry Kasatkin <d.kasatkin@...sung.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	akpm@...ux-foundation.org, Al Viro <viro@...iv.linux.org.uk>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Re: IMA: kernel reading files opened with O_DIRECT

On 2 July 2014 21:45, Jeff Moyer <jmoyer@...hat.com> wrote:
> Christoph Hellwig <hch@...radead.org> writes:
>
>> On Wed, Jul 02, 2014 at 11:55:41AM -0400, Jeff Moyer wrote:
>>> It's acceptable.
>>
>> It's not because it will then also affect other reads going on at the
>> same time.
>

> OK, that part I was fuzzy on.  I wasn't sure if they were preventing
> other reads/writes to the same file somehow.  I should have mentioned
> that.
>
> Cheers,
> Jeff


What Christoph says is not very correct.

At open there cannot be any reads going on at the same time. IMA
reading is guarded by mutex. Following opens do not perform any IMA
readings and do not do what he says...

If file was modified with direct-io, VFS code itself always invalidate
pages before and after any write. It is basically what Christoph says.
But that is not IMA problem but direct-io itself. As it is stupid
interface. I would be more looking to kind of fadvise interface to
control amount of page caching...

So I think what Jeff suggest suites well to IMA.

-- 
Thanks,
Dmitry
--
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/