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

[Matthew Garrett]

From: David Howells <dhowe...@redhat.com>

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

Signed-off-by: David Howells <dhowe...@redhat.com>
Signed-off-by: Matthew Garrett <mj...@google.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Arnaldo Carvalho de Melo <a...@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