linux-kernel - [PATCH 04/11] ACPI: Limit access to custom

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Message-Id: <1346774117-2277-5-git-send-email-mjg@redhat.com>
Date:	Tue,  4 Sep 2012 11:55:10 -0400
From:	Matthew Garrett <mjg@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	Matthew Garrett <mjg@...hat.com>
Subject: [PATCH 04/11] ACPI: Limit access to custom_method

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@...hat.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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