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@xxxxxxxxxxxxxxx>
>> ---
>> 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
