Re: [PATCH V31 19/25] x86/mmiotrace: Lock down the testmmiotrace module
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2019-03-27 15:57:54
Also in:
linux-security-module, lkml
On Tue, 26 Mar 2019 11:27:35 -0700 Matthew Garrett [off-list ref] wrote:
From: David Howells <dhowells@redhat.com> 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. This is a runtime check rather than buildtime in order to allow configurations where the same kernel may be run in both locked down or permissive modes depending on local policy.
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> I'm curious. Should there be a mode to lockdown the tracefs directory too? As that can expose addresses. -- Steve
quoted hunk ↗ jump to hunk
Suggested-by: Thomas Gleixner <redacted> Signed-off-by: David Howells <dhowells@redhat.com Signed-off-by: Matthew Garrett <redacted> cc: Thomas Gleixner <redacted> cc: Steven Rostedt <rostedt@goodmis.org> cc: Ingo Molnar <mingo@kernel.org> cc: "H. Peter Anvin" <hpa@zytor.com> cc: x86@kernel.org --- 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..9e8ad665f354 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", LOCKDOWN_INTEGRITY)) + 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");