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    Subject[PATCH 20/27] x86/mmiotrace: Lock down the testmmiotrace module
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    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.

    Suggested-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: David Howells <dhowells@redhat.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
    Signed-off-by: Matthew Garrett <matthewgarrett@google.com>
    ---
    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");
    --
    2.21.0.392.gf8f6787159e-goog
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