Linux-parisc archive on lore.kernel.org
 help / color / Atom feed
From: Stephen Smalley <sds@tycho.nsa.gov>
To: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	"jani.nikula@linux.intel.com" <jani.nikula@linux.intel.com>,
	"joonas.lahtinen@linux.intel.com"
	<joonas.lahtinen@linux.intel.com>,
	"rodrigo.vivi@intel.com" <rodrigo.vivi@intel.com>,
	"benh@kernel.crashing.org" <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	"james.bottomley@hansenpartnership.com" 
	<james.bottomley@hansenpartnership.com>,
	Serge Hallyn <serge@hallyn.com>, James Morris <jmorris@namei.org>,
	Will Deacon <will.deacon@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Robert Richter <rric@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
	Andi Kleen <ak@linux.intel.com>,
	Stephane Eranian <eranian@google.com>,
	Igor Lubashev <ilubashe@akamai.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Song Liu <songliubraving@fb.com>,
	Lionel Landwerlin <lionel.g.landwerlin@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"linux-security-module@vger.kernel.org" 
	<linux-security-module@vger.kernel.org>,
	"selinux@vger.kernel.org" <selinux@vger.kernel.org>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	"linux-parisc@vger.kernel.org" <linux-parisc@vger.kernel.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	"linux-perf-users@vger.kernel.org"
	<linux-perf-users@vger.kernel.org>,
	oprofile-list@lists.sf.net, Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space
Date: Wed, 12 Feb 2020 12:09:27 -0500
Message-ID: <46751eb9-deca-53cc-95fb-1602cfdf62a2@tycho.nsa.gov> (raw)
In-Reply-To: <950cc6a4-5823-d607-1210-6f62c96cf67f@linux.intel.com>

On 2/12/20 11:56 AM, Alexey Budankov wrote:
> 
> 
> On 12.02.2020 18:45, Stephen Smalley wrote:
>> On 2/12/20 10:21 AM, Stephen Smalley wrote:
>>> On 2/12/20 8:53 AM, Alexey Budankov wrote:
>>>> On 12.02.2020 16:32, Stephen Smalley wrote:
>>>>> On 2/12/20 3:53 AM, Alexey Budankov wrote:
>>>>>> Hi Stephen,
>>>>>>
>>>>>> On 22.01.2020 17:07, Stephen Smalley wrote:
>>>>>>> On 1/22/20 5:45 AM, Alexey Budankov wrote:
>>>>>>>>
>>>>>>>> On 21.01.2020 21:27, Alexey Budankov wrote:
>>>>>>>>>
>>>>>>>>> On 21.01.2020 20:55, Alexei Starovoitov wrote:
>>>>>>>>>> On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov
>>>>>>>>>> <alexey.budankov@linux.intel.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On 21.01.2020 17:43, Stephen Smalley wrote:
>>>>>>>>>>>> On 1/20/20 6:23 AM, Alexey Budankov wrote:
>>>>>>>>>>>>>
>>>>>> <SNIP>
>>>>>>>>>>>>> Introduce CAP_PERFMON capability designed to secure system performance
>>>>>>>>>>>>
>>>>>>>>>>>> Why _noaudit()?  Normally only used when a permission failure is non-fatal to the operation.  Otherwise, we want the audit message.
>>>>>>>>
>>>>>>>> So far so good, I suggest using the simplest version for v6:
>>>>>>>>
>>>>>>>> static inline bool perfmon_capable(void)
>>>>>>>> {
>>>>>>>>        return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN);
>>>>>>>> }
>>>>>>>>
>>>>>>>> It keeps the implementation simple and readable. The implementation is more
>>>>>>>> performant in the sense of calling the API - one capable() call for CAP_PERFMON
>>>>>>>> privileged process.
>>>>>>>>
>>>>>>>> Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes,
>>>>>>>> but this bloating also advertises and leverages using more secure CAP_PERFMON
>>>>>>>> based approach to use perf_event_open system call.
>>>>>>>
>>>>>>> I can live with that.  We just need to document that when you see both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process, try only allowing CAP_PERFMON first and see if that resolves the issue.  We have a similar issue with CAP_DAC_READ_SEARCH versus CAP_DAC_OVERRIDE.
>>>>>>
>>>>>> I am trying to reproduce this double logging with CAP_PERFMON.
>>>>>> I am using the refpolicy version with enabled perf_event tclass [1], in permissive mode.
>>>>>> When running perf stat -a I am observing this AVC audit messages:
>>>>>>
>>>>>> type=AVC msg=audit(1581496695.666:8691): avc:  denied  { open } for  pid=2779 comm="perf" scontext=user_u:user_r:user_systemd_t tcontext=user_u:user_r:user_systemd_t tclass=perf_event permissive=1
>>>>>> type=AVC msg=audit(1581496695.666:8691): avc:  denied  { kernel } for  pid=2779 comm="perf" scontext=user_u:user_r:user_systemd_t tcontext=user_u:user_r:user_systemd_t tclass=perf_event permissive=1
>>>>>> type=AVC msg=audit(1581496695.666:8691): avc:  denied  { cpu } for  pid=2779 comm="perf" scontext=user_u:user_r:user_systemd_t tcontext=user_u:user_r:user_systemd_t tclass=perf_event permissive=1
>>>>>> type=AVC msg=audit(1581496695.666:8692): avc:  denied  { write } for  pid=2779 comm="perf" scontext=user_u:user_r:user_systemd_t tcontext=user_u:user_r:user_systemd_t tclass=perf_event permissive=1
>>>>>>
>>>>>> However there is no capability related messages around. I suppose my refpolicy should
>>>>>> be modified somehow to observe capability related AVCs.
>>>>>>
>>>>>> Could you please comment or clarify on how to enable caps related AVCs in order
>>>>>> to test the concerned logging.
>>>>>
>>>>> The new perfmon permission has to be defined in your policy; you'll have a message in dmesg about "Permission perfmon in class capability2 not defined in policy.".  You can either add it to the common cap2 definition in refpolicy/policy/flask/access_vectors and rebuild your policy or extract your base module as CIL, add it there, and insert the updated module.
>>>>
>>>> Yes, I already have it like this:
>>>> common cap2
>>>> {
>>>> <------>mac_override<--># unused by SELinux
>>>> <------>mac_admin
>>>> <------>syslog
>>>> <------>wake_alarm
>>>> <------>block_suspend
>>>> <------>audit_read
>>>> <------>perfmon
>>>> }
>>>>
>>>> dmesg stopped reporting perfmon as not defined but audit.log still doesn't report CAP_PERFMON denials.
>>>> BTW, audit even doesn't report CAP_SYS_ADMIN denials, however perfmon_capable() does check for it.
>>>
>>> Some denials may be silenced by dontaudit rules; semodule -DB will strip those and semodule -B will restore them.  Other possibility is that the process doesn't have CAP_PERFMON in its effective set and therefore never reaches SELinux at all; denied first by the capability module.
>>
>> Also, the fact that your denials are showing up in user_systemd_t suggests that something is off in your policy or userspace/distro; I assume that is a domain type for the systemd --user instance, but your shell and commands shouldn't be running in that domain (user_t would be more appropriate for that).
> 
> It is user_t for local terminal session:
> ps -Z
> LABEL                             PID TTY          TIME CMD
> user_u:user_r:user_t            11317 pts/9    00:00:00 bash
> user_u:user_r:user_t            11796 pts/9    00:00:00 ps
> 
> For local terminal root session:
> ps -Z
> LABEL                             PID TTY          TIME CMD
> user_u:user_r:user_su_t          2926 pts/3    00:00:00 bash
> user_u:user_r:user_su_t         10995 pts/3    00:00:00 ps
> 
> For remote ssh session:
> ps -Z
> LABEL                             PID TTY          TIME CMD
> user_u:user_r:user_t             7540 pts/8    00:00:00 ps
> user_u:user_r:user_systemd_t     8875 pts/8    00:00:00 bash

That's a bug in either your policy or your userspace/distro integration. 
  In any event, unless user_systemd_t is allowed all capability2 
permissions by your policy, you should see the denials if CAP_PERFMON is 
set in the effective capability set of the process.


  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-20 11:18 [PATCH v5 0/10] Introduce CAP_PERFMON to secure system performance monitoring and observability Alexey Budankov
2020-01-20 11:23 ` [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space Alexey Budankov
2020-01-21 14:43   ` Stephen Smalley
2020-01-21 17:30     ` Alexey Budankov
2020-01-21 17:55       ` Alexei Starovoitov
2020-01-21 18:27         ` Alexey Budankov
2020-01-22 10:45           ` Alexey Budankov
2020-01-22 14:07             ` Stephen Smalley
2020-01-22 14:25               ` Alexey Budankov
2020-02-06 18:03                 ` Alexey Budankov
2020-02-07 11:38                   ` Thomas Gleixner
2020-02-07 13:39                     ` Alexey Budankov
2020-02-20 13:05                       ` Alexey Budankov
2020-02-12  8:53               ` Alexey Budankov
2020-02-12 13:32                 ` Stephen Smalley
2020-02-12 13:53                   ` Alexey Budankov
2020-02-12 15:21                     ` Stephen Smalley
2020-02-12 15:45                       ` Stephen Smalley
2020-02-12 16:56                         ` Alexey Budankov
2020-02-12 17:09                           ` Stephen Smalley [this message]
2020-02-13  9:05                             ` Alexey Budankov
2020-02-12 16:16                       ` Alexey Budankov
2020-01-20 11:24 ` [PATCH v5 02/10] perf/core: open access to the core for CAP_PERFMON privileged process Alexey Budankov
2020-01-20 11:26 ` [PATCH v5 03/10] perf/core: open access to anon probes " Alexey Budankov
2020-01-20 11:27 ` [PATCH v5 04/10] perf tool: extend Perf tool with CAP_PERFMON capability support Alexey Budankov
2020-01-20 11:28 ` [PATCH v5 05/10] drm/i915/perf: open access for CAP_PERFMON privileged process Alexey Budankov
2020-01-20 11:29 ` [PATCH v5 06/10] trace/bpf_trace: " Alexey Budankov
2020-01-20 11:30 ` [PATCH v5 07/10] powerpc/perf: " Alexey Budankov
2020-01-22 11:02   ` Anju T Sudhakar
2020-01-20 11:31 ` [PATCH v5 08/10] parisc/perf: " Alexey Budankov
2020-01-20 11:32 ` [PATCH v5 09/10] drivers/perf: " Alexey Budankov
2020-01-20 11:33 ` [PATCH v5 10/10] drivers/oprofile: " Alexey Budankov

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=46751eb9-deca-53cc-95fb-1602cfdf62a2@tycho.nsa.gov \
    --to=sds@tycho.nsa.gov \
    --cc=acme@kernel.org \
    --cc=ak@linux.intel.com \
    --cc=alexander.shishkin@linux.intel.com \
    --cc=alexei.starovoitov@gmail.com \
    --cc=alexey.budankov@linux.intel.com \
    --cc=ast@kernel.org \
    --cc=benh@kernel.crashing.org \
    --cc=eranian@google.com \
    --cc=ilubashe@akamai.com \
    --cc=intel-gfx@lists.freedesktop.org \
    --cc=james.bottomley@hansenpartnership.com \
    --cc=jani.nikula@linux.intel.com \
    --cc=jmorris@namei.org \
    --cc=jolsa@redhat.com \
    --cc=joonas.lahtinen@linux.intel.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-parisc@vger.kernel.org \
    --cc=linux-perf-users@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=lionel.g.landwerlin@intel.com \
    --cc=luto@amacapital.net \
    --cc=mark.rutland@arm.com \
    --cc=mingo@redhat.com \
    --cc=mpe@ellerman.id.au \
    --cc=namhyung@kernel.org \
    --cc=oprofile-list@lists.sf.net \
    --cc=paulus@samba.org \
    --cc=peterz@infradead.org \
    --cc=rodrigo.vivi@intel.com \
    --cc=rric@kernel.org \
    --cc=selinux@vger.kernel.org \
    --cc=serge@hallyn.com \
    --cc=songliubraving@fb.com \
    --cc=tglx@linutronix.de \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-parisc archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-parisc/0 linux-parisc/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-parisc linux-parisc/ https://lore.kernel.org/linux-parisc \
		linux-parisc@vger.kernel.org
	public-inbox-index linux-parisc

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-parisc


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git