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Subject: [PATCH v6 06/10] trace/bpf_trace: open access for CAP_PERFMON
 privileged process
From:   Alexey Budankov <alexey.budankov@linux.intel.com>
To:     James Morris <jmorris@namei.org>, Serge Hallyn <serge@hallyn.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Peter Zijlstra <peterz@infradead.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        "joonas.lahtinen@linux.intel.com" <joonas.lahtinen@linux.intel.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Will Deacon <will@kernel.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     Andi Kleen <ak@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Stephane Eranian <eranian@google.com>,
        Igor Lubashev <ilubashe@akamai.com>,
        Jiri Olsa <jolsa@redhat.com>,
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References: <576a6141-36d4-14c0-b395-8d195892b916@linux.intel.com>
Organization: Intel Corp.
Message-ID: <d0c5ef3d-92e1-26f5-422a-abe683fb5299@linux.intel.com>
Date:   Wed, 5 Feb 2020 20:34:24 +0300
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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 principal 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>
---
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 e5ef4ae9edb5..334f1d71ebb1 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1395,7 +1395,7 @@ 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;
-- 
2.20.1