acpi: Disable APEI error injection if the kernel is locked down

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>
Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0056-acpi-Disable-APEI-error-injection-if-the-kernel-is-l.patch

diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
index ec50c32ea3da0496ca20e7d7fe8e7970b4cbd124..e082718d01c2b3f2b15f4b5729f8f6a9f8cd82fe 100644 (file)
--- 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())
+               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)))