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From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
        Clark Williams <williams@redhat.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        Alexey Budankov <alexey.budankov@linux.intel.com>,
        James Morris <jamorris@linux.microsoft.com>,
        Song Liu <songliubraving@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Igor Lubashev <ilubashe@akamai.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Serge Hallyn <serge@hallyn.com>,
        Stephane Eranian <eranian@google.com>,
        intel-gfx@lists.freedesktop.org, linux-doc@vger.kernel.org,
        linux-man@vger.kernel.org, linux-security-module@vger.kernel.org,
        selinux@vger.kernel.org, Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: [PATCH 10/60] trace/bpf_trace: Open access for CAP_PERFMON privileged process
Date:   Mon, 20 Apr 2020 08:52:26 -0300
Message-Id: <20200420115316.18781-11-acme@kernel.org>
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From: Alexey Budankov <alexey.budankov@linux.intel.com>

Open access to bpf_trace monitoring for CAP_PERFMON privileged process.
Providing the access under CAP_PERFMON capability singly, without the
rest of CAP_SYS_ADMIN credentials, excludes chances to misuse the
credentials and makes operation more secure.

CAP_PERFMON implements the principle of least privilege for performance
monitoring and observability operations (POSIX IEEE 1003.1e 2.2.2.39
principle of least privilege: A security design principle that states
that a process or program be granted only those privileges (e.g.,
capabilities) necessary to accomplish its legitimate function, and only
for the time that such privileges are actually required)

For backward compatibility reasons access to bpf_trace monitoring
remains open for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN
usage for secure bpf_trace monitoring is discouraged with respect to
CAP_PERFMON capability.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Song Liu <songliubraving@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Igor Lubashev <ilubashe@akamai.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: intel-gfx@lists.freedesktop.org
Cc: linux-doc@vger.kernel.org
Cc: linux-man@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: selinux@vger.kernel.org
Link: http://lore.kernel.org/lkml/c0a0ae47-8b6e-ff3e-416b-3cd1faaf71c0@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 kernel/trace/bpf_trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index ca1796747a77..d7d88007dc6d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1468,7 +1468,7 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
 	u32 *ids, prog_cnt, ids_len;
 	int ret;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!perfmon_capable())
 		return -EPERM;
 	if (event->attr.type != PERF_TYPE_TRACEPOINT)
 		return -EINVAL;
-- 
2.21.1