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    Subject[PATCH 15/24] acpi: Disable APEI error injection if the kernel is locked down
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    From: Linn Crosetto <linn@hpe.com>

    ACPI provides an error injection mechanism, EINJ, for debugging and testing
    the ACPI Platform Error Interface (APEI) and other RAS features. If
    supported by the firmware, ACPI specification 5.0 and later provide for a
    way to specify a physical memory address to which to inject the error.

    Injecting errors through EINJ can produce errors which to the platform are
    indistinguishable from real hardware errors. This can have undesirable
    side-effects, such as causing the platform to mark hardware as needing
    replacement.

    While it does not provide a method to load unauthenticated privileged code,
    the effect of these errors may persist across reboots and affect trust in
    the underlying hardware, so disable error injection through EINJ if
    the kernel is locked down.

    Signed-off-by: Linn Crosetto <linn@hpe.com>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
    cc: linux-acpi@vger.kernel.org
    ---

    drivers/acpi/apei/einj.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
    index b38737c83a24..6d71e1e97b20 100644
    --- a/drivers/acpi/apei/einj.c
    +++ b/drivers/acpi/apei/einj.c
    @@ -518,6 +518,9 @@ static int einj_error_inject(u32 type, u32 flags, u64 param1, u64 param2,
    int rc;
    u64 base_addr, size;

    + if (kernel_is_locked_down("ACPI error injection"))
    + return -EPERM;
    +
    /* If user manually set "flags", make sure it is legal */
    if (flags && (flags &
    ~(SETWA_FLAGS_APICID|SETWA_FLAGS_MEM|SETWA_FLAGS_PCIE_SBDF)))
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