From df7d76ae50f18d4465e59fdf7f19d3df44906cb5 Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Mon, 21 Nov 2016 23:55:55 +0000
Subject: [PATCH 07/32] efi: Add EFI_SECURE_BOOT bit
UEFI machines can be booted in Secure Boot mode. Add a EFI_SECURE_BOOT bit
that can be passed to efi_enabled() to find out whether secure boot is
enabled.
This will be used by the SysRq+x handler, registered by the x86 arch, to find
out whether secure boot mode is enabled so that it can be disabled.
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
arch/x86/kernel/setup.c | 1 +
include/linux/efi.h | 1 +
2 files changed, 2 insertions(+)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 69780ed..447905e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1182,6 +1182,7 @@ void __init setup_arch(char **cmdline_p)
pr_info("Secure boot disabled\n");
break;
case efi_secureboot_mode_enabled:
+ set_bit(EFI_SECURE_BOOT, &efi.flags);
pr_info("Secure boot enabled\n");
break;
default:
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 94d34e0..6049600 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1069,6 +1069,7 @@ extern int __init efi_setup_pcdp_console(char *);
#define EFI_DBG 8 /* Print additional debug info at runtime */
#define EFI_NX_PE_DATA 9 /* Can runtime data regions be mapped non-executable? */
#define EFI_MEM_ATTR 10 /* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */
+#define EFI_SECURE_BOOT 11 /* Are we in Secure Boot mode? */
#ifdef CONFIG_EFI
/*
--
2.7.4
From f05a90c19a9613d8d50597319ed91f691e25b689 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Mon, 21 Nov 2016 23:36:17 +0000
Subject: [PATCH 09/32] Add the ability to lock down access to the running
kernel image
Provide a single call to allow kernel code to determine whether the system
should be locked down, thereby disallowing various accesses that might
allow the running kernel image to be changed including the loading of
modules that aren't validly signed with a key we recognise, fiddling with
MSR registers and disallowing hibernation,
Signed-off-by: David Howells <dhowells@redhat.com>
---
include/linux/kernel.h | 9 +++++++++
include/linux/security.h | 11 +++++++++++
security/Kconfig | 15 +++++++++++++++
security/Makefile | 3 +++
security/lock_down.c | 40 ++++++++++++++++++++++++++++++++++++++++
5 files changed, 78 insertions(+)
create mode 100644 security/lock_down.c
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index cb09238..3cd3be9 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -273,6 +273,15 @@ extern int oops_may_print(void);
void do_exit(long error_code) __noreturn;
void complete_and_exit(struct completion *, long) __noreturn;
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern bool kernel_is_locked_down(void);
+#else
+static inline bool kernel_is_locked_down(void)
+{
+ return false;
+}
+#endif
+
/* Internal, do not use. */
int __must_check _kstrtoul(const char *s, unsigned int base, unsigned long *res);
int __must_check _kstrtol(const char *s, unsigned int base, long *res);
diff --git a/include/linux/security.h b/include/linux/security.h
index d3868f2..187b74b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1679,5 +1679,16 @@ static inline void free_secdata(void *secdata)
{ }
#endif /* CONFIG_SECURITY */
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern void lock_kernel_down(void);
+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT
+extern void lift_kernel_lockdown(void);
+#endif
+#else
+static inline void lock_kernel_down(void)
+{
+}
+#endif
+
#endif /* ! __LINUX_SECURITY_H */
diff --git a/security/Kconfig b/security/Kconfig
index d900f47..d9b391d 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -193,6 +193,21 @@ config STATIC_USERMODEHELPER_PATH
If you wish for all usermode helper programs to be disabled,
specify an empty string here (i.e. "").
+config LOCK_DOWN_KERNEL
+ bool "Allow the kernel to be 'locked down'"
+ help
+ Allow the kernel to be locked down under certain circumstances, for
+ instance if UEFI secure boot is enabled. Locking down the kernel
+ turns off various features that might otherwise allow access to the
+ kernel image (eg. setting MSR registers).
+
+config ALLOW_LOCKDOWN_LIFT
+ bool
+ help
+ Allow the lockdown on a kernel to be lifted, thereby restoring the
+ ability of userspace to access the kernel image (eg. by SysRq+x under
+ x86).
+
source security/selinux/Kconfig
source security/smack/Kconfig
source security/tomoyo/Kconfig
diff --git a/security/Makefile b/security/Makefile
index f2d71cd..8c4a43e 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -29,3 +29,6 @@ obj-$(CONFIG_CGROUP_DEVICE) += device_cgroup.o
# Object integrity file lists
subdir-$(CONFIG_INTEGRITY) += integrity
obj-$(CONFIG_INTEGRITY) += integrity/
+
+# Allow the kernel to be locked down
+obj-$(CONFIG_LOCK_DOWN_KERNEL) += lock_down.o
diff --git a/security/lock_down.c b/security/lock_down.c
new file mode 100644
index 0000000..5788c60
--- /dev/null
+++ b/security/lock_down.c
@@ -0,0 +1,40 @@
+/* Lock down the kernel
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/security.h>
+#include <linux/export.h>
+
+static __read_mostly bool kernel_locked_down;
+
+/*
+ * Put the kernel into lock-down mode.
+ */
+void lock_kernel_down(void)
+{
+ kernel_locked_down = true;
+}
+
+/*
+ * Take the kernel out of lockdown mode.
+ */
+void lift_kernel_lockdown(void)
+{
+ kernel_locked_down = false;
+}
+
+/**
+ * kernel_is_locked_down - Find out if the kernel is locked down
+ */
+bool kernel_is_locked_down(void)
+{
+ return kernel_locked_down;
+}
+EXPORT_SYMBOL(kernel_is_locked_down);
--
2.7.4
From fb6feb38e297260d050fc477c72683ac51d07ae3 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Mon, 21 Nov 2016 23:55:55 +0000
Subject: [PATCH 10/32] efi: Lock down the kernel if booted in secure boot mode
UEFI Secure Boot provides a mechanism for ensuring that the firmware will
only load signed bootloaders and kernels. Certain use cases may also
require that all kernel modules also be signed. Add a configuration option
that to lock down the kernel - which includes requiring validly signed
modules - if the kernel is secure-booted.
Signed-off-by: David Howells <dhowells@redhat.com>
---
arch/x86/Kconfig | 12 ++++++++++++
arch/x86/kernel/setup.c | 8 +++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 874c123..a315974 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1816,6 +1816,18 @@ config EFI_MIXED
If unsure, say N.
+config EFI_SECURE_BOOT_LOCK_DOWN
+ def_bool n
+ depends on EFI
+ prompt "Lock down the kernel when UEFI Secure Boot is enabled"
+ ---help---
+ UEFI Secure Boot provides a mechanism for ensuring that the firmware
+ will only load signed bootloaders and kernels. Certain use cases may
+ also require that all kernel modules also be signed and that
+ userspace is prevented from directly changing the running kernel
+ image. Say Y here to automatically lock down the kernel when a
+ system boots with UEFI Secure Boot enabled.
+
config SECCOMP
def_bool y
prompt "Enable seccomp to safely compute untrusted bytecode"
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 447905e..d44e60e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -69,6 +69,7 @@
#include <linux/crash_dump.h>
#include <linux/tboot.h>
#include <linux/jiffies.h>
+#include <linux/security.h>
#include <linux/usb/xhci-dbgp.h>
#include <video/edid.h>
@@ -1183,7 +1184,12 @@ void __init setup_arch(char **cmdline_p)
break;
case efi_secureboot_mode_enabled:
set_bit(EFI_SECURE_BOOT, &efi.flags);
- pr_info("Secure boot enabled\n");
+ if (IS_ENABLED(CONFIG_EFI_SECURE_BOOT_LOCK_DOWN)) {
+ lock_kernel_down();
+ pr_info("Secure boot enabled and kernel locked down\n");
+ } else {
+ pr_info("Secure boot enabled\n");
+ }
break;
default:
pr_info("Secure boot could not be determined\n");
--
2.7.4
From 7182f2f5b254d6dc6d3105d2f99219a76adf9de0 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Wed, 23 Nov 2016 13:22:22 +0000
Subject: [PATCH 11/32] Enforce module signatures if the kernel is locked down
If the kernel is locked down, require that all modules have valid
signatures that we can verify.
Signed-off-by: David Howells <dhowells@redhat.com>
---
kernel/module.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/module.c b/kernel/module.c
index 7eba6de..3331f2e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2756,7 +2756,7 @@ static int module_sig_check(struct load_info *info, int flags)
}
/* Not having a signature is only an error if we're strict. */
- if (err == -ENOKEY && !sig_enforce)
+ if (err == -ENOKEY && !sig_enforce && !kernel_is_locked_down())
err = 0;
return err;
--
2.7.4
From 7e97c58bcd0b4c082b889fb093a2779147532b9f Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 12/32] Restrict /dev/mem and /dev/kmem when the kernel is
locked down
Allowing users to write to address space makes it possible for the kernel to
be subverted, avoiding module loading restrictions. Prevent this when the
kernel has been locked down.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
drivers/char/mem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 6d9cc2d..f814404 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -163,6 +163,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
if (p != *ppos)
return -EFBIG;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
if (!valid_phys_addr_range(p, count))
return -EFAULT;
@@ -513,6 +516,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
int err = 0;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
if (p < (unsigned long) high_memory) {
unsigned long to_write = min_t(unsigned long, count,
(unsigned long)high_memory - p);
--
2.7.4
From b83b68a9a13120664eaabf21a7b3ff0b065bd5b2 Mon Sep 17 00:00:00 2001
From: Kyle McMartin <kyle@redhat.com>
Date: Mon, 21 Nov 2016 23:55:56 +0000
Subject: [PATCH 13/32] Add a sysrq option to exit secure boot mode
Make sysrq+x exit secure boot mode on x86_64, thereby allowing the running
kernel image to be modified. This lifts the lockdown.
Signed-off-by: David Howells <dhowells@redhat.com>
---
arch/x86/Kconfig | 10 ++++++++++
arch/x86/kernel/setup.c | 31 +++++++++++++++++++++++++++++++
drivers/input/misc/uinput.c | 1 +
drivers/tty/sysrq.c | 19 +++++++++++++------
include/linux/input.h | 5 +++++
include/linux/sysrq.h | 8 +++++++-
kernel/debug/kdb/kdb_main.c | 2 +-
7 files changed, 68 insertions(+), 8 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a315974..6931e68 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1828,6 +1828,16 @@ config EFI_SECURE_BOOT_LOCK_DOWN
image. Say Y here to automatically lock down the kernel when a
system boots with UEFI Secure Boot enabled.
+config EFI_ALLOW_SECURE_BOOT_EXIT
+ def_bool n
+ depends on EFI_SECURE_BOOT_LOCK_DOWN && MAGIC_SYSRQ
+ select ALLOW_LOCKDOWN_LIFT
+ prompt "Allow secure boot mode to be exited with SysRq+x on a keyboard"
+ ---help---
+ Allow secure boot mode to be exited and the kernel lockdown lifted by
+ typing SysRq+x on a keyboard attached to the system (not permitted
+ through procfs).
+
config SECCOMP
def_bool y
prompt "Enable seccomp to safely compute untrusted bytecode"
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index d44e60e..f7635d0 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -71,6 +71,11 @@
#include <linux/jiffies.h>
#include <linux/security.h>
+#include <linux/fips.h>
+#include <linux/cred.h>
+#include <linux/sysrq.h>
+#include <linux/init_task.h>
+
#include <linux/usb/xhci-dbgp.h>
#include <video/edid.h>
@@ -1328,6 +1333,32 @@ void __init i386_reserve_resources(void)
#endif /* CONFIG_X86_32 */
+#ifdef CONFIG_EFI_ALLOW_SECURE_BOOT_EXIT
+
+static void sysrq_handle_secure_boot(int key)
+{
+ if (!efi_enabled(EFI_SECURE_BOOT))
+ return;
+
+ pr_info("Secure boot disabled\n");
+ lift_kernel_lockdown();
+}
+static struct sysrq_key_op secure_boot_sysrq_op = {
+ .handler = sysrq_handle_secure_boot,
+ .help_msg = "unSB(x)",
+ .action_msg = "Disabling Secure Boot restrictions",
+ .enable_mask = SYSRQ_DISABLE_USERSPACE,
+};
+static int __init secure_boot_sysrq(void)
+{
+ if (efi_enabled(EFI_SECURE_BOOT))
+ register_sysrq_key('x', &secure_boot_sysrq_op);
+ return 0;
+}
+late_initcall(secure_boot_sysrq);
+#endif /*CONFIG_EFI_ALLOW_SECURE_BOOT_EXIT*/
+
+
static struct notifier_block kernel_offset_notifier = {
.notifier_call = dump_kernel_offset
};
diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 022be0e..4a054a5 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -387,6 +387,7 @@ static int uinput_allocate_device(struct uinput_device *udev)
if (!udev->dev)
return -ENOMEM;
+ udev->dev->flags |= INPUTDEV_FLAGS_SYNTHETIC;
udev->dev->event = uinput_dev_event;
input_set_drvdata(udev->dev, udev);
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 7113674..e1addc3 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -479,6 +479,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
/* x: May be registered on mips for TLB dump */
/* x: May be registered on ppc/powerpc for xmon */
/* x: May be registered on sparc64 for global PMU dump */
+ /* x: May be registered on x86_64 for disabling secure boot */
NULL, /* x */
/* y: May be registered on sparc64 for global register dump */
NULL, /* y */
@@ -522,7 +523,7 @@ static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
sysrq_key_table[i] = op_p;
}
-void __handle_sysrq(int key, bool check_mask)
+void __handle_sysrq(int key, unsigned int from)
{
struct sysrq_key_op *op_p;
int orig_log_level;
@@ -542,11 +543,15 @@ void __handle_sysrq(int key, bool check_mask)
op_p = __sysrq_get_key_op(key);
if (op_p) {
+ /* Ban synthetic events from some sysrq functionality */
+ if ((from == SYSRQ_FROM_PROC || from == SYSRQ_FROM_SYNTHETIC) &&
+ op_p->enable_mask & SYSRQ_DISABLE_USERSPACE)
+ printk("This sysrq operation is disabled from userspace.\n");
/*
* Should we check for enabled operations (/proc/sysrq-trigger
* should not) and is the invoked operation enabled?
*/
- if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
+ if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) {
pr_cont("%s\n", op_p->action_msg);
console_loglevel = orig_log_level;
op_p->handler(key);
@@ -578,7 +583,7 @@ void __handle_sysrq(int key, bool check_mask)
void handle_sysrq(int key)
{
if (sysrq_on())
- __handle_sysrq(key, true);
+ __handle_sysrq(key, SYSRQ_FROM_KERNEL);
}
EXPORT_SYMBOL(handle_sysrq);
@@ -659,7 +664,7 @@ static void sysrq_do_reset(unsigned long _state)
static void sysrq_handle_reset_request(struct sysrq_state *state)
{
if (state->reset_requested)
- __handle_sysrq(sysrq_xlate[KEY_B], false);
+ __handle_sysrq(sysrq_xlate[KEY_B], SYSRQ_FROM_KERNEL);
if (sysrq_reset_downtime_ms)
mod_timer(&state->keyreset_timer,
@@ -810,8 +815,10 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
default:
if (sysrq->active && value && value != 2) {
+ int from = sysrq->handle.dev->flags & INPUTDEV_FLAGS_SYNTHETIC ?
+ SYSRQ_FROM_SYNTHETIC : 0;
sysrq->need_reinject = false;
- __handle_sysrq(sysrq_xlate[code], true);
+ __handle_sysrq(sysrq_xlate[code], from);
}
break;
}
@@ -1095,7 +1102,7 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
if (get_user(c, buf))
return -EFAULT;
- __handle_sysrq(c, false);
+ __handle_sysrq(c, SYSRQ_FROM_PROC);
}
return count;
diff --git a/include/linux/input.h b/include/linux/input.h
index a65e3b2..8b03571 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -42,6 +42,7 @@ struct input_value {
* @phys: physical path to the device in the system hierarchy
* @uniq: unique identification code for the device (if device has it)
* @id: id of the device (struct input_id)
+ * @flags: input device flags (SYNTHETIC, etc.)
* @propbit: bitmap of device properties and quirks
* @evbit: bitmap of types of events supported by the device (EV_KEY,
* EV_REL, etc.)
@@ -124,6 +125,8 @@ struct input_dev {
const char *uniq;
struct input_id id;
+ unsigned int flags;
+
unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];
unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
@@ -190,6 +193,8 @@ struct input_dev {
};
#define to_input_dev(d) container_of(d, struct input_dev, dev)
+#define INPUTDEV_FLAGS_SYNTHETIC 0x000000001
+
/*
* Verify that we are in sync with input_device_id mod_devicetable.h #defines
*/
diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h
index 387fa7d..f7c52a9 100644
--- a/include/linux/sysrq.h
+++ b/include/linux/sysrq.h
@@ -28,6 +28,8 @@
#define SYSRQ_ENABLE_BOOT 0x0080
#define SYSRQ_ENABLE_RTNICE 0x0100
+#define SYSRQ_DISABLE_USERSPACE 0x00010000
+
struct sysrq_key_op {
void (*handler)(int);
char *help_msg;
@@ -42,8 +44,12 @@ struct sysrq_key_op {
* are available -- else NULL's).
*/
+#define SYSRQ_FROM_KERNEL 0x0001
+#define SYSRQ_FROM_PROC 0x0002
+#define SYSRQ_FROM_SYNTHETIC 0x0004
+
void handle_sysrq(int key);
-void __handle_sysrq(int key, bool check_mask);
+void __handle_sysrq(int key, unsigned int from);
int register_sysrq_key(int key, struct sysrq_key_op *op);
int unregister_sysrq_key(int key, struct sysrq_key_op *op);
struct sysrq_key_op *__sysrq_get_key_op(int key);
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index ca18391..c4524b8 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1967,7 +1967,7 @@ static int kdb_sr(int argc, const char **argv)
return KDB_ARGCOUNT;
kdb_trap_printk++;
- __handle_sysrq(*argv[1], check_mask);
+ __handle_sysrq(*argv[1], check_mask ? SYSRQ_FROM_KERNEL : 0);
kdb_trap_printk--;
return 0;
--
2.7.4
From 8884bd44932e595323fcddfb09c2a2a586134cdf Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 14/32] kexec: Disable at runtime if the kernel is locked down
kexec permits the loading and execution of arbitrary code in ring 0, which
is something that lock-down is meant to prevent. It makes sense to disable
kexec in this situation.
This does not affect kexec_file_load() which can check for a signature on the
image to be booted.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
kernel/kexec.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 980936a..46de8e6 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -194,6 +194,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
return -EPERM;
/*
+ * kexec can be used to circumvent module loading restrictions, so
+ * prevent loading in that case
+ */
+ if (kernel_is_locked_down())
+ return -EPERM;
+
+ /*
* Verify we have a legal set of flags
* This leaves us room for future extensions.
*/
--
2.7.4
From cace563d1743c3d2faf1e46bd4df8e63e2310207 Mon Sep 17 00:00:00 2001
From: Dave Young <dyoung@redhat.com>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 15/32] Copy secure_boot flag in boot params across kexec
reboot
Kexec reboot in case secure boot being enabled does not keep the secure
boot mode in new kernel, so later one can load unsigned kernel via legacy
kexec_load. In this state, the system is missing the protections provided
by secure boot.
Adding a patch to fix this by retain the secure_boot flag in original
kernel.
secure_boot flag in boot_params is set in EFI stub, but kexec bypasses the
stub. Fixing this issue by copying secure_boot flag across kexec reboot.
Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
arch/x86/kernel/kexec-bzimage64.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index d0a814a..3551bca 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -179,6 +179,7 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
if (efi_enabled(EFI_OLD_MEMMAP))
return 0;
+ params->secure_boot = boot_params.secure_boot;
ei->efi_loader_signature = current_ei->efi_loader_signature;
ei->efi_systab = current_ei->efi_systab;
ei->efi_systab_hi = current_ei->efi_systab_hi;
--
2.7.4
From 08a3467acbc28bb469d1eebd0f5fd40b944d984a Mon Sep 17 00:00:00 2001
From: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
Date: Wed, 23 Nov 2016 13:49:19 +0000
Subject: [PATCH 16/32] kexec_file: Disable at runtime if securelevel has been
set
When KEXEC_VERIFY_SIG is not enabled, kernel should not loads image
through kexec_file systemcall if securelevel has been set.
This code was showed in Matthew's patch but not in git:
https://lkml.org/lkml/2015/3/13/778
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
kernel/kexec_file.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index b56a558..003cade 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -268,6 +268,12 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
return -EPERM;
+ /* Don't permit images to be loaded into trusted kernels if we're not
+ * going to verify the signature on them
+ */
+ if (!IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG) && kernel_is_locked_down())
+ return -EPERM;
+
/* Make sure we have a legal set of flags */
if (flags != (flags & KEXEC_FILE_FLAGS))
return -EINVAL;
--
2.7.4
From 925fd10d7a99a6f999dde76daf2b1ef1238b251a Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 17/32] hibernate: Disable when the kernel is locked down
There is currently no way to verify the resume image when returning
from hibernate. This might compromise the signed modules trust model,
so until we can work with signed hibernate images we disable it when the
kernel is locked down.
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
kernel/power/hibernate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 86385af..1629798 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -67,7 +67,7 @@ static const struct platform_hibernation_ops *hibernation_ops;
bool hibernation_available(void)
{
- return (nohibernate == 0);
+ return nohibernate == 0 && !kernel_is_locked_down();
}
/**
--
2.7.4
From b14fb5fcd60c84a09a15bd7ec974b6fbce68335c Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@srcf.ucam.org>
Date: Wed, 23 Nov 2016 13:28:17 +0000
Subject: [PATCH 18/32] uswsusp: Disable when the kernel is locked down
uswsusp allows a user process to dump and then restore kernel state, which
makes it possible to modify the running kernel. Disable this if the kernel
is locked down.
Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
kernel/power/user.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 22df9f7..e4b926d 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *inode, struct file *filp)
if (!hibernation_available())
return -EPERM;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
lock_system_sleep();
if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
--
2.7.4
From d8167273e7562e5aa866d2b65e25bb1962de972c Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 19/32] PCI: Lock down BAR access when the kernel is locked
down
Any hardware that can potentially generate DMA has to be locked down in
order to avoid it being possible for an attacker to modify kernel code,
allowing them to circumvent disabled module loading or module signing.
Default to paranoid - in future we can potentially relax this for
sufficiently IOMMU-isolated devices.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
drivers/pci/pci-sysfs.c | 9 +++++++++
drivers/pci/proc.c | 8 +++++++-
drivers/pci/syscall.c | 2 +-
3 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 0666287..b10992c 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -718,6 +718,9 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
loff_t init_off = off;
u8 *data = (u8 *) buf;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
if (off > dev->cfg_size)
return 0;
if (off + count > dev->cfg_size) {
@@ -1009,6 +1012,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
enum pci_mmap_state mmap_type;
struct resource *res = &pdev->resource[bar];
+ if (kernel_is_locked_down())
+ return -EPERM;
+
if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
return -EINVAL;
@@ -1108,6 +1114,9 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
struct bin_attribute *attr, char *buf,
loff_t off, size_t count)
{
+ if (kernel_is_locked_down())
+ return -EPERM;
+
return pci_resource_io(filp, kobj, attr, buf, off, count, true);
}
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index f82710a..139d6f0 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -116,6 +116,9 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
int size = dev->cfg_size;
int cnt;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
if (pos >= size)
return 0;
if (nbytes >= size)
@@ -195,6 +198,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
#endif /* HAVE_PCI_MMAP */
int ret = 0;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
switch (cmd) {
case PCIIOC_CONTROLLER:
ret = pci_domain_nr(dev->bus);
@@ -233,7 +239,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
struct pci_filp_private *fpriv = file->private_data;
int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
- if (!capable(CAP_SYS_RAWIO))
+ if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
return -EPERM;
if (fpriv->mmap_state == pci_mmap_io) {
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index 9bf993e..c095247 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -92,7 +92,7 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
u32 dword;
int err = 0;
- if (!capable(CAP_SYS_ADMIN))
+ if (!capable(CAP_SYS_ADMIN) || kernel_is_locked_down())
return -EPERM;
dev = pci_get_bus_and_slot(bus, dfn);
--
2.7.4
From 169d13e0c5240ac6aad13aace5ecbdb3de2cfada Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 20/32] x86: Lock down IO port access when the kernel is locked
down
IO port access would permit users to gain access to PCI configuration
registers, which in turn (on a lot of hardware) give access to MMIO
register space. This would potentially permit root to trigger arbitrary
DMA, so lock it down by default.
This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
KDDISABIO console ioctls.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
arch/x86/kernel/ioport.c | 4 ++--
drivers/char/mem.c | 2 ++
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index b01bc8517..4ccaace 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -29,7 +29,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
return -EINVAL;
- if (turn_on && !capable(CAP_SYS_RAWIO))
+ if (turn_on && (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down()))
return -EPERM;
/*
@@ -113,7 +113,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
return -EINVAL;
/* Trying to gain more privileges? */
if (level > old) {
- if (!capable(CAP_SYS_RAWIO))
+ if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
return -EPERM;
}
regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index f814404..9afebb6 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -741,6 +741,8 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
static int open_port(struct inode *inode, struct file *filp)
{
+ if (kernel_is_locked_down())
+ return -EPERM;
return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}
--
2.7.4
From efd24f7e9af624b62f39efce4f60b31f0ca643d8 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:17 +0000
Subject: [PATCH 21/32] x86: Restrict MSR access when the kernel is locked down
Writing to MSRs should not be allowed if the kernel is locked down, since
it could lead to execution of arbitrary code in kernel mode. Based on a
patch by Kees Cook.
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
arch/x86/kernel/msr.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index ef68880..fbcce02 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -84,6 +84,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
int err = 0;
ssize_t bytes = 0;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
if (count % 8)
return -EINVAL; /* Invalid chunk size */
@@ -131,6 +134,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
err = -EBADF;
break;
}
+ if (kernel_is_locked_down()) {
+ err = -EPERM;
+ break;
+ }
if (copy_from_user(®s, uregs, sizeof regs)) {
err = -EFAULT;
break;
--
2.7.4
From 62ebdffbcb0726b98562e9f1173a6d5967755764 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 22/32] asus-wmi: Restrict debugfs interface when the kernel is
locked down
We have no way of validating what all of the Asus WMI methods do on a given
machine - and there's a risk that some will allow hardware state to be
manipulated in such a way that arbitrary code can be executed in the
kernel, circumventing module loading restrictions. Prevent that if the
kernel is locked down.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
drivers/platform/x86/asus-wmi.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 43cb680..9be3e08 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1898,6 +1898,9 @@ static int show_dsts(struct seq_file *m, void *data)
int err;
u32 retval = -1;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
if (err < 0)
@@ -1914,6 +1917,9 @@ static int show_devs(struct seq_file *m, void *data)
int err;
u32 retval = -1;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
&retval);
@@ -1938,6 +1944,9 @@ static int show_call(struct seq_file *m, void *data)
union acpi_object *obj;
acpi_status status;
+ if (kernel_is_locked_down())
+ return -EPERM;
+
status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
1, asus->debug.method_id,
&input, &output);
--
2.7.4
From 31f493d03dde1854fa9e540f87a751fbeeb41cb9 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 23/32] ACPI: Limit access to custom_method when the kernel is
locked down
custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to circumvent restrictions on module loading.
Disable it if the kernel is locked down.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.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 c68e724..e4d721c 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 (kernel_is_locked_down())
+ return -EPERM;
+
if (!(*ppos)) {
/* parse the table header to get the table length */
if (count <= sizeof(struct acpi_table_header))
--
2.7.4
From 1dec5dc62c78f78b9efe44aac3d6119d97b67017 Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@redhat.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 24/32] acpi: Ignore acpi_rsdp kernel param when the kernel has
been locked down
This option allows userspace to pass the RSDP address to the kernel, which
makes it possible for a user to circumvent any restrictions imposed on
loading modules. Ignore the option when the kernel is locked down.
Signed-off-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
drivers/acpi/osl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index db78d35..d4d4ba3 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -192,7 +192,7 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
acpi_physical_address pa = 0;
#ifdef CONFIG_KEXEC
- if (acpi_rsdp)
+ if (acpi_rsdp && !kernel_is_locked_down())
return acpi_rsdp;
#endif
--
2.7.4
From 96eaf04100d7365d93f898013175351c7d2702a6 Mon Sep 17 00:00:00 2001
From: Linn Crosetto <linn@hpe.com>
Date: Wed, 23 Nov 2016 13:32:27 +0000
Subject: [PATCH 25/32] acpi: Disable ACPI table override if the kernel is
locked down
From the kernel documentation (initrd_table_override.txt):
If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible
to override nearly any ACPI table provided by the BIOS with an
instrumented, modified one.
When securelevel is set, the kernel should disallow any unauthenticated
changes to kernel space. ACPI tables contain code invoked by the kernel,
so do not allow ACPI tables to be overridden if the kernel is locked down.
Signed-off-by: Linn Crosetto <linn@hpe.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
drivers/acpi/tables.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
index 2604189..601096d 100644
--- a/drivers/acpi/tables.c
+++ b/drivers/acpi/tables.c
@@ -542,6 +542,11 @@ void __init acpi_table_upgrade(void)
if (table_nr == 0)
return;
+ if (kernel_is_locked_down()) {
+ pr_notice("kernel is locked down, ignoring table override\n");
+ return;
+ }
+
acpi_tables_addr =
memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS,
all_tables_size, PAGE_SIZE);
--
2.7.4
From 521979b819b853f7578ba8edef8b33bc2077026d Mon Sep 17 00:00:00 2001
From: Linn Crosetto <linn@hpe.com>
Date: Wed, 23 Nov 2016 13:39:41 +0000
Subject: [PATCH 26/32] 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>
---
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 ec50c32..e082718 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)))
--
2.7.4
From fe597dad1cba83345d62c4079c0d8861c426698c Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@coreos.com>
Date: Wed, 23 Nov 2016 13:41:23 +0000
Subject: [PATCH 27/32] Enable cold boot attack mitigation
---
arch/x86/boot/compressed/eboot.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 801c7a1..ef9409b 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -604,6 +604,31 @@ void setup_graphics(struct boot_params *boot_params)
}
}
+#define MEMORY_ONLY_RESET_CONTROL_GUID \
+ EFI_GUID (0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29)
+
+static void enable_reset_attack_mitigation(void)
+{
+ static const efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID;
+ static const efi_char16_t MemoryOverwriteRequestControl_name[] = {
+ 'M', 'e', 'm', 'o', 'r', 'y',
+ 'O', 'v', 'e', 'r', 'w', 'r', 'i', 't', 'e',
+ 'R', 'e', 'q', 'u', 'e', 's', 't',
+ 'C', 'o', 'n', 't', 'r', 'o', 'l',
+ 0
+ };
+ u8 val = 1;
+
+ /* Ignore the return value here - there's not really a lot we can do */
+ efi_call_runtime(set_variable,
+ (efi_char16_t *)MemoryOverwriteRequestControl_name,
+ (efi_guid_t *)&var_guid,
+ EFI_VARIABLE_NON_VOLATILE |
+ EFI_VARIABLE_BOOTSERVICE_ACCESS |
+ EFI_VARIABLE_RUNTIME_ACCESS,
+ sizeof(val), val);
+}
+
/*
* Because the x86 boot code expects to be passed a boot_params we
* need to create one ourselves (usually the bootloader would create
@@ -988,6 +1013,9 @@ struct boot_params *efi_main(struct efi_config *c,
else
setup_boot_services32(efi_early);
+ /* Ask the firmware to clear memory if we don't have a clean shutdown */
+ enable_reset_attack_mitigation();
+
/*
* If the boot loader gave us a value for secure_boot then we use that,
* otherwise we ask the BIOS.
--
2.7.4
From 04fac895731801bc6cb26a6061f1c353c80a866c Mon Sep 17 00:00:00 2001
From: "Lee, Chun-Yi" <jlee@suse.com>
Date: Wed, 23 Nov 2016 13:52:16 +0000
Subject: [PATCH 28/32] bpf: Restrict kernel image access functions when the
kernel is locked down
There are some bpf functions can be used to read kernel memory:
bpf_probe_read, bpf_probe_write_user and bpf_trace_printk. These allow
private keys in kernel memory (e.g. the hibernation image signing key) to
be read by an eBPF program. Prohibit those functions when the kernel is
locked down.
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
kernel/trace/bpf_trace.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index cee9802..7fde851 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -65,6 +65,11 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
{
int ret;
+ if (kernel_is_locked_down()) {
+ memset(dst, 0, size);
+ return -EPERM;
+ }
+
ret = probe_kernel_read(dst, unsafe_ptr, size);
if (unlikely(ret < 0))
memset(dst, 0, size);
@@ -84,6 +89,9 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
u32, size)
{
+ if (kernel_is_locked_down())
+ return -EPERM;
+
/*
* Ensure we're in user context which is safe for the helper to
* run. This helper has no business in a kthread.
@@ -143,6 +151,9 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
if (fmt[--fmt_size] != 0)
return -EINVAL;
+ if (kernel_is_locked_down())
+ return __trace_printk(1, fmt, 0, 0, 0);
+
/* check format string for allowed specifiers */
for (i = 0; i < fmt_size; i++) {
if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
--
2.7.4
From 707d0e14c2c0d6c3139ff4bcb16ee22c462b4304 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Tue, 22 Nov 2016 10:10:34 +0000
Subject: [PATCH 29/32] scsi: Lock down the eata driver
When the kernel is running in secure boot mode, we lock down the kernel to
prevent userspace from modifying the running kernel image. Whilst this
includes prohibiting access to things like /dev/mem, it must also prevent
access by means of configuring driver modules in such a way as to cause a
device to access or modify the kernel image.
The eata driver takes a single string parameter that contains a slew of
settings, including hardware resource configuration. Prohibit use of the
parameter if the kernel is locked down.
Suggested-by: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Dario Ballabio <ballabio_dario@emc.com>
cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
cc: "Martin K. Petersen" <martin.petersen@oracle.com>
cc: linux-scsi@vger.kernel.org
---
drivers/scsi/eata.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/eata.c b/drivers/scsi/eata.c
index 227dd2c..5c036d10 100644
--- a/drivers/scsi/eata.c
+++ b/drivers/scsi/eata.c
@@ -1552,8 +1552,13 @@ static int eata2x_detect(struct scsi_host_template *tpnt)
tpnt->proc_name = "eata2x";
- if (strlen(boot_options))
+ if (strlen(boot_options)) {
+ if (kernel_is_locked_down()) {
+ pr_err("Command line-specified device addresses, irqs and dma channels are not permitted when the kernel is locked down\n");
+ return -EPERM;
+ }
option_setup(boot_options);
+ }
#if defined(MODULE)
/* io_port could have been modified when loading as a module */
--
2.7.4
From 07e05e0b7d806a05eba55092630bb75a92311344 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 25 Nov 2016 14:37:45 +0000
Subject: [PATCH 30/32] Prohibit PCMCIA CIS storage when the kernel is locked
down
Prohibit replacement of the PCMCIA Card Information Structure when the
kernel is locked down.
Signed-off-by: David Howells <dhowells@redhat.com>
---
drivers/pcmcia/cistpl.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/pcmcia/cistpl.c b/drivers/pcmcia/cistpl.c
index 55ef7d1..193e4f7 100644
--- a/drivers/pcmcia/cistpl.c
+++ b/drivers/pcmcia/cistpl.c
@@ -1578,6 +1578,11 @@ static ssize_t pccard_store_cis(struct file *filp, struct kobject *kobj,
struct pcmcia_socket *s;
int error;
+ if (kernel_is_locked_down()) {
+ pr_err("Direct CIS storage isn't permitted when the kernel is locked down\n");
+ return -EPERM;
+ }
+
s = to_socket(container_of(kobj, struct device, kobj));
if (off)
--
2.7.4
From cf1e877adbe35c5f72a9d85570b494aa3f35be6a Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Wed, 7 Dec 2016 10:28:39 +0000
Subject: [PATCH 31/32] Lock down TIOCSSERIAL
Lock down TIOCSSERIAL as that can be used to change the ioport and irq
settings on a serial port. This only appears to be an issue for the serial
drivers that use the core serial code. All other drivers seem to either
ignore attempts to change port/irq or give an error.
Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
drivers/tty/serial/serial_core.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 9939c3d..7c040e2 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -820,6 +820,12 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
new_flags = new_info->flags;
old_custom_divisor = uport->custom_divisor;
+ if ((change_port || change_irq) && kernel_is_locked_down()) {
+ pr_err("Using TIOCSSERIAL to change device addresses, irqs and dma channels is not permitted when the kernel is locked down\n");
+ retval = -EPERM;
+ goto exit;
+ }
+
if (!capable(CAP_SYS_ADMIN)) {
retval = -EPERM;
if (change_irq || change_port ||
--
2.7.4