From: Alexey Budankov <alexey.budankov@linux.intel.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Andi Kleen <ak@linux.intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
"selinux@vger.kernel.org" <selinux@vger.kernel.org>,
"linux-security-module@vger.kernel.org"
<linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v2 3/4] perf tool: make Perf tool aware of SELinux access control
Date: Thu, 23 Apr 2020 17:58:11 +0300 [thread overview]
Message-ID: <12d614d9-e77f-d96b-7546-7b59f06edabf@linux.intel.com> (raw)
In-Reply-To: <20200423132733.GC19437@kernel.org>
On 23.04.2020 16:27, Arnaldo Carvalho de Melo wrote:
> Em Wed, Apr 22, 2020 at 05:45:34PM +0300, Alexey Budankov escreveu:
>>
>> Implement SELinux sysfs check to see if the system is in enforcing
>> mode and print warning message with pointers to check audit logs.
>>
>> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
>> ---
>> tools/perf/util/cloexec.c | 4 ++--
>> tools/perf/util/evsel.c | 40 +++++++++++++++++++++++----------------
>> 2 files changed, 26 insertions(+), 18 deletions(-)
>>
>> diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
>> index a12872f2856a..9c8ec816261b 100644
>> --- a/tools/perf/util/cloexec.c
>> +++ b/tools/perf/util/cloexec.c
>> @@ -65,7 +65,7 @@ static int perf_flag_probe(void)
>> return 1;
>> }
>>
>> - WARN_ONCE(err != EINVAL && err != EBUSY,
>> + WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
>> "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
>> err, str_error_r(err, sbuf, sizeof(sbuf)));
>>
>> @@ -83,7 +83,7 @@ static int perf_flag_probe(void)
>> if (fd >= 0)
>> close(fd);
>>
>> - if (WARN_ONCE(fd < 0 && err != EBUSY,
>> + if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
>> "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
>> err, str_error_r(err, sbuf, sizeof(sbuf))))
>> return -1;
>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>> index 9fa92649adb4..82492ca12405 100644
>> --- a/tools/perf/util/evsel.c
>> +++ b/tools/perf/util/evsel.c
>> @@ -2514,32 +2514,40 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
>> int err, char *msg, size_t size)
>> {
>> char sbuf[STRERR_BUFSIZE];
>> - int printed = 0;
>> + int printed = 0, enforced = 0;
>>
>> switch (err) {
>> case EPERM:
>> case EACCES:
>> + printed += scnprintf(msg + printed, size - printed,
>> + "Access to performance monitoring and observability operations is limited.\n");
>> +
>> + if (!sysfs__read_int("fs/selinux/enforce", &enforced)) {
>> + if (enforced) {
>> + printed += scnprintf(msg + printed, size - printed,
>> + "Enforced MAC policy settings (SELinux) can limit access to performance\n"
>> + "monitoring and observability operations. Inspect system audit records for\n"
>> + "more perf_event access control information and adjusting the policy.\n");
>> + }
>> + }
>> +
>> if (err == EPERM)
>> - printed = scnprintf(msg, size,
>> - "No permission to enable %s event.\n\n",
>> + printed += scnprintf(msg, size,
>> + "No permission to enable %s event.\n",
>> perf_evsel__name(evsel));
>
> This removal of a newline doesn't seem necessary to this patch.
There will be break in the middle of the message then, but ok.
>
>> return scnprintf(msg + printed, size - printed,
>> - "You may not have permission to collect %sstats.\n\n"
>> - "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
>> - "which controls use of the performance events system by\n"
>> - "unprivileged users (without CAP_PERFMON or CAP_SYS_ADMIN).\n\n"
>> - "The current value is %d:\n\n"
>> + "Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open\n"
>> + "access to performance monitoring and observability operations for users\n"
>> + "without CAP_PERFMON capability. perf_event_paranoid setting is %d:\n"
>
> Here we need as well to check if the kernel/libcap supports CAP_PERFMON
> to provide a better error message.
I will change change "CAP_PERFMON" to "CAP_PERFMON or CAP_SYS_ADMIN" in the new message.
>
>> " -1: Allow use of (almost) all events by all users\n"
>> " Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n"
>> - ">= 0: Disallow ftrace function tracepoint by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
>> - " Disallow raw tracepoint access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
>> - ">= 1: Disallow CPU event access by users without CAP_PERFMON or CAP_SYS_ADMIN\n"
>> - ">= 2: Disallow kernel profiling by users without CAP_PERFMON or CAP_SYS_ADMIN\n\n"
>> - "To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n"
>> - " kernel.perf_event_paranoid = -1\n" ,
>> - target->system_wide ? "system-wide " : "",
>> - perf_event_paranoid());
>> + ">= 0: Disallow raw and ftrace function tracepoint access\n"
>> + ">= 1: Disallow CPU event access\n"
>> + ">= 2: Disallow kernel profiling\n"
>> + "To make the adjusted perf_event_paranoid setting permanent preserve it\n"
>> + "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)",
>> + perf_event_paranoid());
>> case ENOENT:
>> return scnprintf(msg, size, "The %s event is not supported.",
>> perf_evsel__name(evsel));
Thanks,
Alexey
next prev parent reply other threads:[~2020-04-23 14:58 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-22 14:40 [PATCH v2 0/4] perf: make Perf tool aware of SELinux access control Alexey Budankov
2020-04-22 14:44 ` [PATCH v2 1/4] perf trace: substitute CAP_SYS_ADMIN with CAP_PERFMON in error message Alexey Budankov
2020-04-23 13:20 ` Arnaldo Carvalho de Melo
2020-04-23 14:49 ` Alexey Budankov
2020-04-23 18:10 ` Arnaldo Carvalho de Melo
2020-04-22 14:44 ` [PATCH v2 2/4] perf docs: substitute CAP_SYS_ADMIN with CAP_PERFMON where needed Alexey Budankov
2020-04-23 13:22 ` Arnaldo Carvalho de Melo
2020-04-23 14:51 ` Alexey Budankov
2020-04-22 14:45 ` [PATCH v2 3/4] perf tool: make Perf tool aware of SELinux access control Alexey Budankov
2020-04-23 13:27 ` Arnaldo Carvalho de Melo
2020-04-23 14:58 ` Alexey Budankov [this message]
2020-04-22 14:47 ` [PATCH v2 4/4] perf docs: introduce security.txt file to document related issues Alexey Budankov
Reply instructions:
You may reply publicly 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=12d614d9-e77f-d96b-7546-7b59f06edabf@linux.intel.com \
--to=alexey.budankov@linux.intel.com \
--cc=ak@linux.intel.com \
--cc=alexander.shishkin@linux.intel.com \
--cc=arnaldo.melo@gmail.com \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=selinux@vger.kernel.org \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).