From: Alexey Budankov <alexey.budankov@linux.intel.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>,
Alexei Starovoitov <ast@kernel.org>,
Ingo Molnar <mingo@redhat.com>, James Morris <jmorris@namei.org>,
Namhyung Kim <namhyung@kernel.org>,
Serge Hallyn <serge@hallyn.com>, Jiri Olsa <jolsa@redhat.com>,
Song Liu <songliubraving@fb.com>, Andi Kleen <ak@linux.intel.com>,
Stephane Eranian <eranian@google.com>,
Igor Lubashev <ilubashe@akamai.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-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
linux-man@vger.kernel.org
Subject: Re: [PATCH v8 00/12] Introduce CAP_PERFMON to secure system performance monitoring and observability
Date: Mon, 13 Jul 2020 15:37:51 +0300 [thread overview]
Message-ID: <0fadcf78-8b0e-ed03-a554-cc172b7d249c@linux.intel.com> (raw)
In-Reply-To: <20200713121746.GA7029@kernel.org>
On 13.07.2020 15:17, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jul 13, 2020 at 12:48:25PM +0300, Alexey Budankov escreveu:
>>
>> On 10.07.2020 20:09, Arnaldo Carvalho de Melo wrote:
>>> Em Fri, Jul 10, 2020 at 05:30:50PM +0300, Alexey Budankov escreveu:
>>>> On 10.07.2020 16:31, Ravi Bangoria wrote:
>>>>>> Currently access to perf_events, i915_perf and other performance
>>>>>> monitoring and observability subsystems of the kernel is open only for
>>>>>> a privileged process [1] with CAP_SYS_ADMIN capability enabled in the
>>>>>> process effective set [2].
>
>>>>>> This patch set introduces CAP_PERFMON capability designed to secure
>>>>>> system performance monitoring and observability operations so that
>>>>>> CAP_PERFMON would assist CAP_SYS_ADMIN capability in its governing role
>>>>>> for performance monitoring and observability subsystems of the kernel.
>
>>>>> I'm seeing an issue with CAP_PERFMON when I try to record data for a
>>>>> specific target. I don't know whether this is sort of a regression or
>>>>> an expected behavior.
>
>>>> Thanks for reporting and root causing this case. The behavior looks like
>>>> kind of expected since currently CAP_PERFMON takes over the related part
>>>> of CAP_SYS_ADMIN credentials only. Actually Perf security docs [1] say
>>>> that access control is also subject to CAP_SYS_PTRACE credentials.
>
>>> I think that stating that in the error message would be helpful, after
>>> all, who reads docs? 8-)
>
>> At least those who write it :D ...
>
> Everybody should read it, sure :-)
>
>>> I.e., this:
>>>
>>> $ ./perf stat ls
>>> Error:
>>> Access to performance monitoring and observability operations is limited.
>>> $
>>>
>>> Could become:
>>>
>>> $ ./perf stat ls
>>> Error:
>>> Access to performance monitoring and observability operations is limited.
>>> Right now only CAP_PERFMON is granted, you may need CAP_SYS_PTRACE.
>>> $
>>
>> It would better provide reference to perf security docs in the tool output.
>
> So add a 3rd line:
>
> $ ./perf stat ls
> Error:
> Access to performance monitoring and observability operations is limited.
> Right now only CAP_PERFMON is granted, you may need CAP_SYS_PTRACE.
> Please read the 'Perf events and tool security' document:
> https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html
If it had that patch below then message change would not be required.
However this two sentences in the end of whole message would still add up:
"Please read the 'Perf events and tool security' document:
https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html"
>
>> Looks like extending ptrace_may_access() check for perf_events with CAP_PERFMON
>
> You mean the following?
Exactly that.
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 856d98c36f56..a2397f724c10 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -11595,7 +11595,7 @@ SYSCALL_DEFINE5(perf_event_open,
> * perf_event_exit_task() that could imply).
> */
> err = -EACCES;
> - if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
> + if (!perfmon_capable() && !ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
> goto err_cred;
> }
>
>> makes monitoring simpler and even more secure to use since Perf tool need
>> not to start/stop/single-step and read/write registers and memory and so on
>> like a debugger or strace-like tool. What do you think?
>
> I tend to agree, Peter?
>
>> Alexei
>>
>>>
>>> - Arnaldo
Alexei
next prev parent reply other threads:[~2020-07-13 12:38 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 8:42 [PATCH v8 00/12] Introduce CAP_PERFMON to secure system performance monitoring and observability Alexey Budankov
2020-04-02 8:45 ` [PATCH v8 01/12] capabilities: introduce CAP_PERFMON to kernel and user space Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] capabilities: Introduce " tip-bot2 for Alexey Budankov
2020-04-02 8:46 ` [PATCH v8 02/12] perf/core: open access to the core for CAP_PERFMON privileged process Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] perf/core: Open " tip-bot2 for Alexey Budankov
2020-04-02 8:47 ` [PATCH v8 03/12] perf/core: open access to probes " Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] " tip-bot2 for Alexey Budankov
2020-04-02 8:47 ` [PATCH v8 04/12] perf tool: extend Perf tool with CAP_PERFMON capability support Alexey Budankov
2020-04-03 11:08 ` Jiri Olsa
2020-04-03 13:08 ` Alexey Budankov
2020-04-04 2:18 ` Namhyung Kim
2020-04-04 8:18 ` Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] perf tools: Support CAP_PERFMON capability tip-bot2 for Alexey Budankov
2020-04-02 8:48 ` [PATCH v8 05/12] drm/i915/perf: open access for CAP_PERFMON privileged process Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] drm/i915/perf: Open " tip-bot2 for Alexey Budankov
2020-04-02 8:48 ` [PATCH v8 06/12] trace/bpf_trace: open " Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] trace/bpf_trace: Open " tip-bot2 for Alexey Budankov
2020-04-02 8:49 ` [PATCH v8 07/12] powerpc/perf: open " Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] " tip-bot2 for Alexey Budankov
2020-04-02 8:50 ` [PATCH v8 08/12] parisc/perf: " Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] " tip-bot2 for Alexey Budankov
2020-04-02 8:51 ` [PATCH v8 09/12] drivers/perf: " Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] drivers/perf: Open " tip-bot2 for Alexey Budankov
2020-04-02 8:53 ` [PATCH v8 10/12] drivers/oprofile: open " Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] drivers/oprofile: Open " tip-bot2 for Alexey Budankov
2020-04-02 8:54 ` [PATCH v8 11/12] doc/admin-guide: update perf-security.rst with CAP_PERFMON information Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] doc/admin-guide: Update " tip-bot2 for Alexey Budankov
2020-04-02 8:54 ` [PATCH v8 12/12] doc/admin-guide: update kernel.rst " Alexey Budankov
2020-04-05 14:10 ` Arnaldo Carvalho de Melo
2020-04-05 14:41 ` Alexey Budankov
2020-04-05 14:54 ` Alexey Budankov
2020-04-05 15:05 ` Arnaldo Carvalho de Melo
2020-04-05 15:51 ` Alexey Budankov
2020-04-22 12:17 ` [tip: perf/core] " tip-bot2 for Alexey Budankov
2020-04-07 14:30 ` [PATCH v8 00/12] Introduce CAP_PERFMON to secure system performance monitoring and observability Arnaldo Carvalho de Melo
2020-04-07 14:35 ` Arnaldo Carvalho de Melo
2020-04-07 14:54 ` Alexey Budankov
2020-04-07 16:36 ` Arnaldo Carvalho de Melo
2020-04-07 16:40 ` Arnaldo Carvalho de Melo
2020-04-07 17:17 ` Alexey Budankov
2020-04-07 16:52 ` Alexey Budankov
2020-04-07 17:02 ` Arnaldo Carvalho de Melo
2020-04-07 17:32 ` Alexey Budankov
2020-04-07 16:56 ` Arnaldo Carvalho de Melo
2020-04-07 17:23 ` Arnaldo Carvalho de Melo
2020-07-10 13:31 ` Ravi Bangoria
2020-07-10 14:30 ` Alexey Budankov
2020-07-10 17:09 ` Arnaldo Carvalho de Melo
2020-07-13 9:48 ` Alexey Budankov
2020-07-13 12:17 ` Arnaldo Carvalho de Melo
2020-07-13 12:37 ` Alexey Budankov [this message]
2020-07-13 18:51 ` Arnaldo Carvalho de Melo
2020-07-14 10:59 ` Peter Zijlstra
2020-07-14 15:27 ` Arnaldo Carvalho de Melo
2020-07-21 13:06 ` Alexey Budankov
2020-07-22 11:30 ` Arnaldo Carvalho de Melo
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