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    Subject[PATCH 04/11] ACPI: Limit access to custom_method
    Date
    It must be impossible for even root to get code executed in kernel context
    under a secure boot environment. custom_method effectively allows arbitrary
    access to system memory, so it needs to have a capability check here.

    Signed-off-by: Matthew Garrett <mjg@redhat.com>
    ---
    drivers/acpi/custom_method.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
    index 5d42c24..3e78014 100644
    --- a/drivers/acpi/custom_method.c
    +++ b/drivers/acpi/custom_method.c
    @@ -29,6 +29,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
    struct acpi_table_header table;
    acpi_status status;

    + if (!capable(CAP_SECURE_FIRMWARE))
    + return -EPERM;
    +
    if (!(*ppos)) {
    /* parse the table header to get the table length */
    if (count <= sizeof(struct acpi_table_header))
    --
    1.7.11.4


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