linux-kernel - [PATCH 19/24] acpi: Disable APEI error injection if the kernel is locked down

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Message-ID: <149141236435.31282.18405211623757724751.stgit@warthog.procyon.org.uk>
Date:   Wed, 05 Apr 2017 18:12:44 +0100
From:   David Howells <dhowells@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     gnomes@...rguk.ukuu.org.uk, linux-efi@...r.kernel.org,
        Linn Crosetto <linn@....com>, matthew.garrett@...ula.com,
        gregkh@...uxfoundation.org, dhowells@...hat.com,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org
Subject: [PATCH 19/24] acpi: Disable APEI error injection if the kernel is
 locked down

From: Linn Crosetto <linn@....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@....com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 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 ec50c32ea3da..e082718d01c2 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())
+		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)))