Messages in this thread | | | Date | Wed, 27 Mar 2019 11:57:49 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH V31 19/25] x86/mmiotrace: Lock down the testmmiotrace module |
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On Tue, 26 Mar 2019 11:27:35 -0700 Matthew Garrett <matthewgarrett@google.com> 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
> Suggested-by: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: David Howells <dhowells@redhat.com > Signed-off-by: Matthew Garrett <mjg59@google.com> > cc: Thomas Gleixner <tglx@linutronix.de> > 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");
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