Enable CONFIG_EFI_TEST as a module (rhbz 1759325)

The driver is needed for testing purposes, enable it on the architectures
where EFI is supported. Also, disallow access to the registered device if
the kernel is locked down.

1 files changed, 87 insertions, 0 deletions

diff --git a/efi-efi_test-lock-down-dev-efi_test-and-require-CAP_.patch b/efi-efi_test-lock-down-dev-efi_test-and-require-CAP_.patch
new file mode 100644
index 000000000..61a52c6fd
--- /dev/null
+++ b/efi-efi_test-lock-down-dev-efi_test-and-require-CAP_.patch
@@ -0,0 +1,87 @@
+From: Javier Martinez Canillas <javierm@redhat.com>
+Subject: [PATCH v2] efi/efi_test: lock down /dev/efi_test and require
+ CAP_SYS_ADMIN
+Date: Tue,  8 Oct 2019 12:55:10 +0200
+
+The driver exposes EFI runtime services to user-space through an IOCTL
+interface, calling the EFI services function pointers directly without
+using the efivar API.
+
+Disallow access to the /dev/efi_test character device when the kernel is
+locked down to prevent arbitrary user-space to call EFI runtime services.
+
+Also require CAP_SYS_ADMIN to open the chardev to prevent unprivileged
+users to call the EFI runtime services, instead of just relying on the
+chardev file mode bits for this.
+
+The main user of this driver is the fwts [0] tool that already checks if
+the effective user ID is 0 and fails otherwise. So this change shouldn't
+cause any regression to this tool.
+
+[0]: https://wiki.ubuntu.com/FirmwareTestSuite/Reference/uefivarinfo
+
+Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
+Acked-by: Laszlo Ersek <lersek@redhat.com>
+Acked-by: Matthew Garrett <mjg59@google.com>
+---
+
+Changes in v2:
+- Also disable /dev/efi_test access when the kernel is locked down as
+  suggested by Matthew Garrett.
+- Add Acked-by tag from Laszlo Ersek.
+
+ drivers/firmware/efi/test/efi_test.c | 8 ++++++++
+ include/linux/security.h             | 1 +
+ security/lockdown/lockdown.c         | 1 +
+ 3 files changed, 10 insertions(+)
+
+diff --git a/drivers/firmware/efi/test/efi_test.c b/drivers/firmware/efi/test/efi_test.c
+index 877745c3aaf..7baf48c01e7 100644
+--- a/drivers/firmware/efi/test/efi_test.c
++++ b/drivers/firmware/efi/test/efi_test.c
+@@ -14,6 +14,7 @@
+ #include <linux/init.h>
+ #include <linux/proc_fs.h>
+ #include <linux/efi.h>
++#include <linux/security.h>
+ #include <linux/slab.h>
+ #include <linux/uaccess.h>
+ 
+@@ -717,6 +718,13 @@ static long efi_test_ioctl(struct file *file, unsigned int cmd,
+ 
+ static int efi_test_open(struct inode *inode, struct file *file)
+ {
++	int ret = security_locked_down(LOCKDOWN_EFI_TEST);
++
++	if (ret)
++		return ret;
++
++	if (!capable(CAP_SYS_ADMIN))
++		return -EACCES;
+ 	/*
+ 	 * nothing special to do here
+ 	 * We do accept multiple open files at the same time as we
+diff --git a/include/linux/security.h b/include/linux/security.h
+index a8d59d612d2..9df7547afc0 100644
+--- a/include/linux/security.h
++++ b/include/linux/security.h
+@@ -105,6 +105,7 @@ enum lockdown_reason {
+ 	LOCKDOWN_NONE,
+ 	LOCKDOWN_MODULE_SIGNATURE,
+ 	LOCKDOWN_DEV_MEM,
++	LOCKDOWN_EFI_TEST,
+ 	LOCKDOWN_KEXEC,
+ 	LOCKDOWN_HIBERNATION,
+ 	LOCKDOWN_PCI_ACCESS,
+diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
+index 8a10b43daf7..40b790536de 100644
+--- a/security/lockdown/lockdown.c
++++ b/security/lockdown/lockdown.c
+@@ -20,6 +20,7 @@ static const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
+ 	[LOCKDOWN_NONE] = "none",
+ 	[LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading",
+ 	[LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
++	[LOCKDOWN_EFI_TEST] = "/dev/efi_test access",
+ 	[LOCKDOWN_KEXEC] = "kexec of unsigned images",
+ 	[LOCKDOWN_HIBERNATION] = "hibernation",
+ 	[LOCKDOWN_PCI_ACCESS] = "direct PCI access",