linux-kernel - Re: [PATCH] RFC: selinux avc trace

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Date:   Thu, 30 Jul 2020 21:12:39 +0200
From:   peter enderborg <peter.enderborg@...y.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     Thiébaud Weksteen <tweek@...gle.com>,
        Paul Moore <paul@...l-moore.com>,
        Nick Kralevich <nnk@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>, <linux-kernel@...r.kernel.org>,
        <selinux@...r.kernel.org>
Subject: Re: [PATCH] RFC: selinux avc trace

On 7/30/20 7:16 PM, Steven Rostedt wrote:
> On Thu, 30 Jul 2020 19:05:49 +0200
> peter enderborg <peter.enderborg@...y.com> wrote:
>
>>>> It should be a full structure with a lot of sub strings.  But that make is even more relevant.  
>>> So one event instance can have a list of strings recorded?  
>> Yes, it is a list very similar to a normal trace. But it is more generic.
>>
>> For example ino= is for filesystems that have inode, but for a
>> violation that send a signal that make no sense at all.  Network
>> addresses is in many cases not applicable. laddr= is only exist for
>> for IP.
>>
>> So if you just print them it will look like:
>>
>> avc:  denied  { find } for interface=vendor.qti.hardware.perf::IPerf sid=u:r:permissioncontroller_app:s0:c230,c256,c512,c768 pid=9164 scontext=u:r:permissioncontroller_app:s0:c230,c256,c512,c768 tcontext=u:object_r:vendor_hal_perf_hwservice:s0 tclass=hwservice_manager permissive=0
>>  avc:  denied  { execute } for  pid=13914 comm="ScionFrontendAp" path="/data/user_de/0/com.google.android.gms/app_chimera/m/00000002/oat/arm64/DynamiteLoader.odex" dev="sda77" ino=204967 scontext=u:r:platform_app:s0:c512,c768 tcontext=u:object_r:privapp_data_file:s0:c512,c768 tclass=file permissive=0 ppid=788 pcomm="main" pgid=13914 pgcomm="on.updatecenter"
>>
>> It omit the fields that are not used. Some parts are common some are not. So a correct format specification for trace will be problematic if there is no "optional" field indicator.
> That's all quite noisy. What is the object of these changes? What
> exactly are you trying to trace and why?

It is noisy, and it have to be. it covers a lot of different areas.  One common problem is
to debug userspace applications regarding violations. You get the violation from the logs
and try to figure out what you did to cause it. With a trace point you can do much better
when combine with other traces. Having a the userspace stack is a very good way,
unfortunately  it does not work on that many architectures within trace.

What exactly are you doing with any trace? You collect data to analyse what's
going on. This is not different. Selinux do a specific thing, but is has lots of parameters.


> -- Steve