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Date:   Tue, 26 Mar 2019 11:27:39 -0700
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Subject: [PATCH V31 23/25] Lock down perf when in confidentiality mode
From:   Matthew Garrett <matthewgarrett@google.com>
To:     jmorris@namei.org
Cc:     linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, dhowells@redhat.com,
        linux-api@vger.kernel.org, luto@kernel.org,
        Matthew Garrett <mjg59@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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From: David Howells <dhowells@redhat.com>

Disallow the use of certain perf facilities that might allow userspace to
access kernel data.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
---
 kernel/events/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3cd13a30f732..6ad3d83c091c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10461,6 +10461,12 @@ SYSCALL_DEFINE5(perf_event_open,
 			return -EINVAL;
 	}
 
+	if ((attr.sample_type & PERF_SAMPLE_REGS_INTR) &&
+	    kernel_is_locked_down("PERF_SAMPLE_REGS_INTR",
+				  LOCKDOWN_CONFIDENTIALITY))
+		/* REGS_INTR can leak data, lockdown must prevent this */
+		return -EPERM;
+
 	/* Only privileged users can get physical addresses */
 	if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
 	    perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
-- 
2.21.0.392.gf8f6787159e-goog