Re: [PATCH v8 00/12] Introduce CAP_PERFMON to secure system performance monitoring and observability

[Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>]

On 07.04.2020 17:35, Arnaldo Carvalho de Melo wrote:
> Em Tue, Apr 07, 2020 at 11:30:14AM -0300, Arnaldo Carvalho de Melo escreveu:
>> [perf@five ~]$ type perf
>> perf is hashed (/home/perf/bin/perf)
>> [perf@five ~]$ getcap /home/perf/bin/perf
>> /home/perf/bin/perf = cap_sys_ptrace,cap_syslog,38+ep
>> [perf@five ~]$ groups
>> perf perf_users
>> [perf@five ~]$ id
>> uid=1002(perf) gid=1002(perf) groups=1002(perf),1003(perf_users) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
>> [perf@five ~]$ perf top --stdio
>> Error:
>> Failed to mmap with 1 (Operation not permitted)
>> [perf@five ~]$ perf record -a
>> ^C[ perf record: Woken up 1 times to write data ]
>> [ perf record: Captured and wrote 1.177 MB perf.data (1552 samples) ]
>>
>> [perf@five ~]$ perf evlist
>> cycles:u
>> [perf@five ~]$
> 
> Humm, perf record falls back to cycles:u after initially trying cycles
> (i.e. kernel and userspace), lemme see trying 'perf top -e cycles:u',
> lemme test, humm not really:
> 
> [perf@five ~]$ perf top --stdio -e cycles:u
> Error:
> Failed to mmap with 1 (Operation not permitted)
> [perf@five ~]$ perf record -e cycles:u -a sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 1.123 MB perf.data (132 samples) ]
> [perf@five ~]$
> 
> Back to debugging this.

Could makes sense adding cap_ipc_lock to the binary to isolate from this:

kernel/events/core.c: 6101
	if ((locked > lock_limit) && perf_is_paranoid() &&
		!capable(CAP_IPC_LOCK)) {
		ret = -EPERM;
		goto unlock;
	}

~Alexey