[PATCH 21/27] x86/mmiotrace: Lock down the testmmiotrace module

From: Matthew Garrett
Date: Thu Feb 28 2019 - 18:13:52 EST


From: David Howells <dhowells@xxxxxxxxxx>

The testmmiotrace module shouldn't be permitted when the kernel is locked
down as it can be used to arbitrarily read and write MMIO space.

Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx
cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
cc: Ingo Molnar <mingo@xxxxxxxxxx>
cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
cc: x86@xxxxxxxxxx
---
arch/x86/mm/testmmiotrace.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
index f6ae6830b341..bbaad357f5d7 100644
--- a/arch/x86/mm/testmmiotrace.c
+++ b/arch/x86/mm/testmmiotrace.c
@@ -115,6 +115,9 @@ static int __init init(void)
{
unsigned long size = (read_far) ? (8 << 20) : (16 << 10);

+ if (kernel_is_locked_down("MMIO trace testing"))
+ return -EPERM;
+
if (mmio_address == 0) {
pr_err("you have to use the module argument mmio_address.\n");
pr_err("DO NOT LOAD THIS MODULE UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!\n");
--
2.21.0.352.gf09ad66450-goog