[PATCH V32 23/27] Lock down perf when in confidentiality mode

[Matthew Garrett]

From: David Howells <dhowells at redhat.com>

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

Signed-off-by: David Howells <dhowells at redhat.com>
Signed-off-by: Matthew Garrett <mjg59 at google.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Arnaldo Carvalho de Melo <acme at 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