linux-kernel - Re: [PATCH V4 2/2] blktrace: allow access trace file in lockdown mode

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Message-ID: <6300a33a-9d3d-42a2-d332-81e02d52d310@oracle.com>
Date:   Wed, 26 Apr 2023 09:32:54 -0700
From:   Junxiao Bi <junxiao.bi@...cle.com>
To:     Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-block@...r.kernel.org
Cc:     paul@...l-moore.com, nathanl@...ux.ibm.com, jmorris@...ei.org,
        serge@...lyn.com, konrad.wilk@...cle.com, joe.jin@...cle.com
Subject: Re: [PATCH V4 2/2] blktrace: allow access trace file in lockdown mode

On 4/25/23 12:12 PM, Jens Axboe wrote:

> On 4/25/23 11:55?AM, Junxiao Bi wrote:
>> Any IO folks can help review this patch?
>>
>> Paul needs a confirm from you that the information blktrace exporting
>> to userspace through the relay files are safe, not leaking information
>> that userspace shouldn't know in lockdown mode.
> I don't know anything about what lockdown is, but in terms of blktrace,
> it is a way to trace meta data associated with IO. It'll tell you things
> like "task T wants to {read,write} on device D, at offset X, and of size
> Y". For passthrough IO, it'll also dump the CDB. There's never any
> actual data traced.

Thanks Jens. Lockdown is a security feature which is trying to limit 
user's(including root) capability to access security sensitive 
information inside kernel, there are two modes, read-only access is 
allowed in "integrity" mode while both read and write access are 
disabled in "confidentiality" mode.

Paul,  do you have any other concerns regarding blktrace? As Jens 
mentioned, blktrace just exported IO metadata to Userspace, those were 
not security sensitive information.

Thanks,

Junxiao.