diff mbox series

[v2,47/57,B] efi/efi_test: Lock down /dev/efi_test and require CAP_SYS_ADMIN

Message ID 20200619161621.644540-48-seth.forshee@canonical.com
State New
Headers show
Series Lockdown updates | expand

Commit Message

Seth Forshee June 19, 2020, 4:16 p.m. UTC 
From: Javier Martinez Canillas <javierm@redhat.com>

BugLink: https://bugs.launchpad.net/bugs/1884159

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>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Matthew Garrett <mjg59@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191029173755.27149-7-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(backported from commit 359efcc2c910117d2faf704ce154e91fc976d37f)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
 drivers/firmware/efi/test/efi_test.c | 7 +++++++
 1 file changed, 7 insertions(+)
diff mbox series

Patch

diff --git a/drivers/firmware/efi/test/efi_test.c b/drivers/firmware/efi/test/efi_test.c
index f61bb52be318..3dc55ac0af73 100644
--- a/drivers/firmware/efi/test/efi_test.c
+++ b/drivers/firmware/efi/test/efi_test.c
@@ -696,6 +696,13 @@  static long efi_test_ioctl(struct file *file, unsigned int cmd,
 
 static int efi_test_open(struct inode *inode, struct file *file)
 {
+	bool locked_down = secure_modules();
+
+	if (locked_down)
+		return -EPERM;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
 	/*
 	 * nothing special to do here
 	 * We do accept multiple open files at the same time as we