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.
> 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.
> " -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));
> --
> 2.24.1
>
>
--
- Arnaldo
