From patchwork Thu Oct 19 14:50:40 2017
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Subject: [01/27] Add the ability to lock down access to the running kernel
image
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017331
Message-Id: <150842463996.7923.6815305873334959305.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:50:40 +0100
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 | 17 +++++++++++++
include/linux/security.h | 8 ++++++
security/Kconfig | 8 ++++++
security/Makefile | 3 ++
security/lock_down.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 96 insertions(+)
create mode 100644 security/lock_down.c
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 0ad4c3044cf9..362da2e4bf53 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -287,6 +287,23 @@ static inline void refcount_error_report(struct pt_regs *regs, const char *err)
{ }
#endif
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern bool __kernel_is_locked_down(const char *what, bool first);
+#else
+static inline bool __kernel_is_locked_down(const char *what, bool first)
+{
+ return false;
+}
+#endif
+
+#define kernel_is_locked_down(what) \
+ ({ \
+ static bool message_given; \
+ bool locked_down = __kernel_is_locked_down(what, !message_given); \
+ message_given = true; \
+ locked_down; \
+ })
+
/* 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 ce6265960d6c..f9a894b42d4c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1753,5 +1753,13 @@ static inline void free_secdata(void *secdata)
{ }
#endif /* CONFIG_SECURITY */
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern void __init init_lockdown(void);
+#else
+static inline void __init init_lockdown(void);
+{
+}
+#endif
+
#endif /* ! __LINUX_SECURITY_H */
diff --git a/security/Kconfig b/security/Kconfig
index e8e449444e65..8e01fd59ae7e 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -205,6 +205,14 @@ 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).
+
source security/selinux/Kconfig
source security/smack/Kconfig
source security/tomoyo/Kconfig
diff --git a/security/Makefile b/security/Makefile
index f2d71cdb8e19..8c4a43e3d4e0 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 000000000000..d8595c0e6673
--- /dev/null
+++ b/security/lock_down.c
@@ -0,0 +1,60 @@
+/* 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 __ro_after_init bool kernel_locked_down;
+
+/*
+ * Put the kernel into lock-down mode.
+ */
+static void __init lock_kernel_down(const char *where)
+{
+ if (!kernel_locked_down) {
+ kernel_locked_down = true;
+ pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n",
+ where);
+ }
+}
+
+static int __init lockdown_param(char *ignored)
+{
+ lock_kernel_down("command line");
+ return 0;
+}
+
+early_param("lockdown", lockdown_param);
+
+/*
+ * Lock the kernel down from very early in the arch setup. This must happen
+ * prior to things like ACPI being initialised.
+ */
+void __init init_lockdown(void)
+{
+#ifdef CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT
+ if (efi_enabled(EFI_SECURE_BOOT))
+ lock_kernel_down("EFI secure boot");
+#endif
+}
+
+/**
+ * kernel_is_locked_down - Find out if the kernel is locked down
+ * @what: Tag to use in notice generated if lockdown is in effect
+ */
+bool __kernel_is_locked_down(const char *what, bool first)
+{
+ if (what && first && kernel_locked_down)
+ pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n",
+ what);
+ return kernel_locked_down;
+}
+EXPORT_SYMBOL(__kernel_is_locked_down);
From patchwork Thu Oct 19 14:50:47 2017
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Subject: [02/27] Add a SysRq option to lift kernel lockdown
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017333
Message-Id: <150842464774.7923.7951986297563109339.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:50:47 +0100
From: Kyle McMartin <kyle@redhat.com>
Make an option to provide a sysrq key that will lift the kernel lockdown,
thereby allowing the running kernel image to be accessed and modified.
On x86_64 this is triggered with SysRq+x, but this key may not be available
on all arches, so it is set by setting LOCKDOWN_LIFT_KEY in asm/setup.h.
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: x86@kernel.org
---
arch/x86/include/asm/setup.h | 2 ++
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 +-
security/Kconfig | 15 +++++++++++++
security/lock_down.c | 48 ++++++++++++++++++++++++++++++++++++++++++
8 files changed, 92 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index a65cf544686a..863f77582c09 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -8,6 +8,8 @@
#include <linux/linkage.h>
#include <asm/page_types.h>
+#define LOCKDOWN_LIFT_KEY 'x'
+
#ifdef __i386__
#include <linux/pfn.h>
diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 443151de90c6..45a1f5460805 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -408,6 +408,7 @@ 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 3ffc1ce29023..8b766dbad6dd 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -481,6 +481,7 @@ 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 */
@@ -524,7 +525,7 @@ 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;
@@ -544,11 +545,15 @@ 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);
@@ -580,7 +585,7 @@ 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);
@@ -661,7 +666,7 @@ 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,
@@ -812,8 +817,10 @@ 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;
}
@@ -1097,7 +1104,7 @@ 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 fb5e23c7ed98..9d2b45a21ade 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 387fa7d05c98..f7c52a9ea394 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 c8146d53ca67..b480cadf9272 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1970,7 +1970,7 @@ 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;
diff --git a/security/Kconfig b/security/Kconfig
index 8e01fd59ae7e..4be6be71e075 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -213,6 +213,21 @@ config LOCK_DOWN_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).
+
+config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
+ bool "Allow the kernel lockdown to be lifted by SysRq"
+ depends on MAGIC_SYSRQ
+ help
+ Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
+ combination on a wired keyboard.
+
+
source security/selinux/Kconfig
source security/smack/Kconfig
source security/tomoyo/Kconfig
diff --git a/security/lock_down.c b/security/lock_down.c
index d8595c0e6673..f71118c340d2 100644
--- a/security/lock_down.c
+++ b/security/lock_down.c
@@ -11,8 +11,13 @@
#include <linux/security.h>
#include <linux/export.h>
+#include <linux/sysrq.h>
+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT
+static __read_mostly bool kernel_locked_down;
+#else
static __ro_after_init bool kernel_locked_down;
+#endif
/*
* Put the kernel into lock-down mode.
@@ -58,3 +63,46 @@ bool __kernel_is_locked_down(const char *what, bool first)
return kernel_locked_down;
}
EXPORT_SYMBOL(__kernel_is_locked_down);
+
+/*
+ * Take the kernel out of lockdown mode.
+ */
+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT
+static void lift_kernel_lockdown(void)
+{
+ pr_notice("Lifting lockdown\n");
+ kernel_locked_down = false;
+}
+#endif
+
+/*
+ * Allow lockdown to be lifted by pressing something like SysRq+x (and not by
+ * echoing the appropriate letter into the sysrq-trigger file).
+ */
+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_KEY
+
+static void sysrq_handle_lockdown_lift(int key)
+{
+ if (kernel_locked_down)
+ lift_kernel_lockdown();
+}
+
+static struct sysrq_key_op lockdown_lift_sysrq_op = {
+ .handler = sysrq_handle_lockdown_lift,
+ .help_msg = "unSB(x)",
+ .action_msg = "Disabling Secure Boot restrictions",
+ .enable_mask = SYSRQ_DISABLE_USERSPACE,
+};
+
+static int __init lockdown_lift_sysrq(void)
+{
+ if (kernel_locked_down) {
+ lockdown_lift_sysrq_op.help_msg[5] = LOCKDOWN_LIFT_KEY;
+ register_sysrq_key(LOCKDOWN_LIFT_KEY, &lockdown_lift_sysrq_op);
+ }
+ return 0;
+}
+
+late_initcall(lockdown_lift_sysrq);
+
+#endif /* CONFIG_ALLOW_LOCKDOWN_LIFT_BY_KEY */
From patchwork Thu Oct 19 14:50:55 2017
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Subject: [03/27] Enforce module signatures if the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017335
Message-Id: <150842465546.7923.6762214527898273559.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:50:55 +0100
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 | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/module.c b/kernel/module.c
index de66ec825992..3d9a3270c179 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2781,7 +2781,8 @@ 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("Loading of unsigned modules"))
err = 0;
return err;
From patchwork Thu Oct 19 14:51:02 2017
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Subject: [04/27] Restrict /dev/mem and /dev/kmem when the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017337
Message-Id: <150842466261.7923.14359746674406637357.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:02 +0100
From: Matthew Garrett <matthew.garrett@nebula.com>
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 593a8818aca9..b7c36898b689 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -179,6 +179,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
if (p != *ppos)
return -EFBIG;
+ if (kernel_is_locked_down("/dev/mem"))
+ return -EPERM;
+
if (!valid_phys_addr_range(p, count))
return -EFAULT;
@@ -540,6 +543,9 @@ 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("/dev/kmem"))
+ return -EPERM;
+
if (p < (unsigned long) high_memory) {
unsigned long to_write = min_t(unsigned long, count,
(unsigned long)high_memory - p);
From patchwork Thu Oct 19 14:51:09 2017
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Subject: [05/27] kexec: Disable at runtime if the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017339
Message-Id: <150842466996.7923.17995994984545441369.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:09 +0100
From: Matthew Garrett <matthew.garrett@nebula.com>
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>
Acked-by: Dave Young <dyoung@redhat.com>
cc: kexec@lists.infradead.org
---
kernel/kexec.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/kexec.c b/kernel/kexec.c
index e62ec4dc6620..7dadfed9b676 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -202,6 +202,13 @@ 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("kexec of unsigned images"))
+ return -EPERM;
+
+ /*
* Verify we have a legal set of flags
* This leaves us room for future extensions.
*/
From patchwork Thu Oct 19 14:51:20 2017
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MIME-Version: 1.0
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Subject: [06/27] Copy secure_boot flag in boot params across kexec reboot
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017341
Message-Id: <150842468009.7923.5512653689857540199.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:20 +0100
From: Dave Young <dyoung@redhat.com>
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>
cc: kexec@lists.infradead.org
---
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 fb095ba0c02f..7d0fac5bcbbe 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;
From patchwork Thu Oct 19 14:51:27 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [07/27] kexec_file: Disable at runtime if securelevel has been set
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017343
Message-Id: <150842468754.7923.10037578333644594134.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:27 +0100
From: Chun-Yi Lee <joeyli.kernel@gmail.com>
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: Chun-Yi Lee <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: kexec@lists.infradead.org
---
kernel/kexec_file.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 9f48f4412297..ff6523f2dcc2 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -255,6 +255,13 @@ 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("kexec of unsigned images"))
+ return -EPERM;
+
/* Make sure we have a legal set of flags */
if (flags != (flags & KEXEC_FILE_FLAGS))
return -EINVAL;
From patchwork Thu Oct 19 14:51:34 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [08/27] hibernate: Disable when the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017345
Message-Id: <150842469486.7923.10376463083069013490.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:34 +0100
From: Josh Boyer <jwboyer@fedoraproject.org>
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>
cc: linux-pm@vger.kernel.org
---
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 a5c36e9c56a6..f2eafefeec50 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -70,7 +70,7 @@ static const struct platform_hibernation_ops *hibernation_ops;
bool hibernation_available(void)
{
- return (nohibernate == 0);
+ return nohibernate == 0 && !kernel_is_locked_down("Hibernation");
}
/**
From patchwork Thu Oct 19 14:51:42 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [09/27] uswsusp: Disable when the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017347
Message-Id: <150842470227.7923.15293760935442172683.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:42 +0100
From: Matthew Garrett <mjg59@srcf.ucam.org>
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>
cc: linux-pm@vger.kernel.org
---
kernel/power/user.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 22df9f7ff672..678ade9decfe 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("/dev/snapshot"))
+ return -EPERM;
+
lock_system_sleep();
if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
From patchwork Thu Oct 19 14:51:49 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [10/27] PCI: Lock down BAR access when the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017349
Message-Id: <150842470945.7923.134066103094708461.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:49 +0100
From: Matthew Garrett <matthew.garrett@nebula.com>
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>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
cc: linux-pci@vger.kernel.org
---
drivers/pci/pci-sysfs.c | 9 +++++++++
drivers/pci/proc.c | 9 ++++++++-
drivers/pci/syscall.c | 3 ++-
3 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 1eecfa301f7f..e1a3b0e765c2 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -881,6 +881,9 @@ 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("Direct PCI access"))
+ return -EPERM;
+
if (off > dev->cfg_size)
return 0;
if (off + count > dev->cfg_size) {
@@ -1175,6 +1178,9 @@ 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("Direct PCI access"))
+ return -EPERM;
+
if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
return -EINVAL;
@@ -1255,6 +1261,9 @@ 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("Direct PCI access"))
+ 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 098360d7ff81..a6c53d855daa 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("Direct PCI access"))
+ 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("Direct PCI access"))
+ return -EPERM;
+
switch (cmd) {
case PCIIOC_CONTROLLER:
ret = pci_domain_nr(dev->bus);
@@ -236,7 +242,8 @@ 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("Direct PCI access"))
return -EPERM;
if (fpriv->mmap_state == pci_mmap_io) {
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index 9bf993e1f71e..afa01cc3ceec 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -92,7 +92,8 @@ 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("Direct PCI access"))
return -EPERM;
dev = pci_get_bus_and_slot(bus, dfn);
From patchwork Thu Oct 19 14:51:56 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [11/27] x86: Lock down IO port access when the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017351
Message-Id: <150842471673.7923.7676307847318724274.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:51:56 +0100
From: Matthew Garrett <matthew.garrett@nebula.com>
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>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
cc: x86@kernel.org
---
arch/x86/kernel/ioport.c | 6 ++++--
drivers/char/mem.c | 2 ++
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 9c3cf0944bce..2c0f058651c5 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -30,7 +30,8 @@ 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("ioperm")))
return -EPERM;
/*
@@ -120,7 +121,8 @@ 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("iopl"))
return -EPERM;
}
regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index b7c36898b689..0875b3d47773 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -768,6 +768,8 @@ 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("Direct ioport access"))
+ return -EPERM;
return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}
From patchwork Thu Oct 19 14:52:04 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [12/27] x86/msr: Restrict MSR access when the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017353
Message-Id: <150842472452.7923.2592278090192179002.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:04 +0100
From: Matthew Garrett <matthew.garrett@nebula.com>
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.
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
cc: x86@kernel.org
---
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 ef688804f80d..a05a97863286 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("Direct MSR access"))
+ 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("Direct MSR access")) {
+ err = -EPERM;
+ break;
+ }
if (copy_from_user(®s, uregs, sizeof regs)) {
err = -EFAULT;
break;
From patchwork Thu Oct 19 14:52:11 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [13/27] asus-wmi: Restrict debugfs interface when the kernel is
locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017355
Message-Id: <150842473184.7923.9538070958624850416.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:11 +0100
From: Matthew Garrett <matthew.garrett@nebula.com>
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>
cc: acpi4asus-user@lists.sourceforge.net
cc: platform-driver-x86@vger.kernel.org
---
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 48e1541dc8d4..ef5587469337 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1905,6 +1905,9 @@ static int show_dsts(struct seq_file *m, void *data)
int err;
u32 retval = -1;
+ if (kernel_is_locked_down("Asus WMI"))
+ return -EPERM;
+
err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
if (err < 0)
@@ -1921,6 +1924,9 @@ static int show_devs(struct seq_file *m, void *data)
int err;
u32 retval = -1;
+ if (kernel_is_locked_down("Asus WMI"))
+ return -EPERM;
+
err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
&retval);
@@ -1945,6 +1951,9 @@ static int show_call(struct seq_file *m, void *data)
union acpi_object *obj;
acpi_status status;
+ if (kernel_is_locked_down("Asus WMI"))
+ return -EPERM;
+
status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
0, asus->debug.method_id,
&input, &output);
From patchwork Thu Oct 19 14:52:19 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [14/27] ACPI: Limit access to custom_method when the kernel is locked
down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017357
Message-Id: <150842473899.7923.6590815561953001126.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:19 +0100
From: Matthew Garrett <matthew.garrett@nebula.com>
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>
cc: linux-acpi@vger.kernel.org
---
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 c68e72414a67..b33fba70ec51 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("ACPI custom methods"))
+ return -EPERM;
+
if (!(*ppos)) {
/* parse the table header to get the table length */
if (count <= sizeof(struct acpi_table_header))
From patchwork Thu Oct 19 14:52:27 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [15/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been
locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017359
Message-Id: <150842474713.7923.4851355698276917280.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:27 +0100
From: Josh Boyer <jwboyer@redhat.com>
This option allows userspace to pass the RSDP address to the kernel, which
makes it possible for a user to modify the workings of hardware . Reject
the option when the kernel is locked down.
Signed-off-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Dave Young <dyoung@redhat.com>
cc: linux-acpi@vger.kernel.org
---
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 db78d353bab1..36c6527c1b0a 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("ACPI RSDP specification"))
return acpi_rsdp;
#endif
From patchwork Thu Oct 19 14:52:34 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [16/27] acpi: Disable ACPI table override if the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017361
Message-Id: <150842475442.7923.12198790224494561644.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:34 +0100
From: Linn Crosetto <linn@hpe.com>
>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>
cc: linux-acpi@vger.kernel.org
---
drivers/acpi/tables.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
index 80ce2a7d224b..5cc13c42daf9 100644
--- a/drivers/acpi/tables.c
+++ b/drivers/acpi/tables.c
@@ -526,6 +526,11 @@ void __init acpi_table_upgrade(void)
if (table_nr == 0)
return;
+ if (kernel_is_locked_down("ACPI table override")) {
+ 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);
From patchwork Thu Oct 19 14:52:41 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [17/27] acpi: Disable APEI error injection if the kernel is locked
down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017363
Message-Id: <150842476188.7923.14340260837257633120.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:41 +0100
From: Linn Crosetto <linn@hpe.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@hpe.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-acpi@vger.kernel.org
---
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 b38737c83a24..6d71e1e97b20 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("ACPI error injection"))
+ 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)))
From patchwork Thu Oct 19 14:52:49 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [18/27] bpf: Restrict kernel image access functions when the kernel
is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017365
Message-Id: <150842476953.7923.18174368926573855810.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:49 +0100
From: Chun-Yi Lee <jlee@suse.com>
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: Chun-Yi Lee <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: netdev@vger.kernel.org
---
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 dc498b605d5d..35e85a3fdb37 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("BPF")) {
+ 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("BPF"))
+ 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("BPF"))
+ 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]))
From patchwork Thu Oct 19 14:52:57 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [19/27] scsi: Lock down the eata driver
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017367
Message-Id: <150842477698.7923.15570916285929038112.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:52:57 +0100
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: Alan Cox <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 | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/eata.c b/drivers/scsi/eata.c
index 6501c330d8c8..72fceaa8f3da 100644
--- a/drivers/scsi/eata.c
+++ b/drivers/scsi/eata.c
@@ -1552,8 +1552,11 @@ 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("Command line-specified device addresses, irqs and dma channels"))
+ return -EPERM;
option_setup(boot_options);
+ }
#if defined(MODULE)
/* io_port could have been modified when loading as a module */
From patchwork Thu Oct 19 14:53:04 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [20/27] Prohibit PCMCIA CIS storage when the kernel is locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017369
Message-Id: <150842478444.7923.5111743275510836636.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:04 +0100
Prohibit replacement of the PCMCIA Card Information Structure when the
kernel is locked down.
Suggested-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-pcmcia@lists.infradead.org
---
drivers/pcmcia/cistpl.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/pcmcia/cistpl.c b/drivers/pcmcia/cistpl.c
index 55ef7d1fd8da..b7a0e42eeb25 100644
--- a/drivers/pcmcia/cistpl.c
+++ b/drivers/pcmcia/cistpl.c
@@ -1578,6 +1578,9 @@ static ssize_t pccard_store_cis(struct file *filp, struct kobject *kobj,
struct pcmcia_socket *s;
int error;
+ if (kernel_is_locked_down("Direct PCMCIA CIS storage"))
+ return -EPERM;
+
s = to_socket(container_of(kobj, struct device, kobj));
if (off)
From patchwork Thu Oct 19 14:53:12 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [21/27] Lock down TIOCSSERIAL
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017371
Message-Id: <150842479208.7923.3429065489239605709.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:12 +0100
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>
cc: Jiri Slaby <jslaby@suse.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 3a14cccbd7ff..41f0922ad842 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -842,6 +842,12 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
new_flags = (__force upf_t)new_info->flags;
old_custom_divisor = uport->custom_divisor;
+ if ((change_port || change_irq) &&
+ kernel_is_locked_down("Using TIOCSSERIAL to change device addresses, irqs and dma channels")) {
+ retval = -EPERM;
+ goto exit;
+ }
+
if (!capable(CAP_SYS_ADMIN)) {
retval = -EPERM;
if (change_irq || change_port ||
From patchwork Thu Oct 19 14:53:19 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [22/27] Lock down module params that specify hardware parameters (eg.
ioport)
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017373
Message-Id: <150842479932.7923.8106830872069353117.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:19 +0100
Provided an annotation for module parameters that specify hardware
parameters (such as io ports, iomem addresses, irqs, dma channels, fixed
dma buffers and other types).
Suggested-by: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
---
kernel/params.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
diff --git a/kernel/params.c b/kernel/params.c
index 60b2d8101355..422979adb60a 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -108,13 +108,19 @@ bool parameq(const char *a, const char *b)
return parameqn(a, b, strlen(a)+1);
}
-static void param_check_unsafe(const struct kernel_param *kp)
+static bool param_check_unsafe(const struct kernel_param *kp,
+ const char *doing)
{
if (kp->flags & KERNEL_PARAM_FL_UNSAFE) {
pr_warn("Setting dangerous option %s - tainting kernel\n",
kp->name);
add_taint(TAINT_USER, LOCKDEP_STILL_OK);
}
+
+ if (kp->flags & KERNEL_PARAM_FL_HWPARAM &&
+ kernel_is_locked_down("Command line-specified device addresses, irqs and dma channels"))
+ return false;
+ return true;
}
static int parse_one(char *param,
@@ -144,8 +150,10 @@ static int parse_one(char *param,
pr_debug("handling %s with %p\n", param,
params[i].ops->set);
kernel_param_lock(params[i].mod);
- param_check_unsafe(¶ms[i]);
- err = params[i].ops->set(val, ¶ms[i]);
+ if (param_check_unsafe(¶ms[i], doing))
+ err = params[i].ops->set(val, ¶ms[i]);
+ else
+ err = -EPERM;
kernel_param_unlock(params[i].mod);
return err;
}
@@ -556,6 +564,12 @@ static ssize_t param_attr_show(struct module_attribute *mattr,
return count;
}
+#ifdef CONFIG_MODULES
+#define mod_name(mod) (mod)->name
+#else
+#define mod_name(mod) "unknown"
+#endif
+
/* sysfs always hands a nul-terminated string in buf. We rely on that. */
static ssize_t param_attr_store(struct module_attribute *mattr,
struct module_kobject *mk,
@@ -568,8 +582,10 @@ static ssize_t param_attr_store(struct module_attribute *mattr,
return -EPERM;
kernel_param_lock(mk->mod);
- param_check_unsafe(attribute->param);
- err = attribute->param->ops->set(buf, attribute->param);
+ if (param_check_unsafe(attribute->param, mod_name(mk->mod)))
+ err = attribute->param->ops->set(buf, attribute->param);
+ else
+ err = -EPERM;
kernel_param_unlock(mk->mod);
if (!err)
return len;
From patchwork Thu Oct 19 14:53:26 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [23/27] x86/mmiotrace: Lock down the testmmiotrace module
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017375
Message-Id: <150842480649.7923.13997201431299349211.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:26 +0100
The testmmiotrace module shouldn't be permitted when the kernel is locked
down as it can be used to arbitrarily read and write MMIO space.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Howells <dhowells@redhat.com
cc: Thomas Gleixner <tglx@linutronix.de>
cc: Steven Rostedt <rostedt@goodmis.org>
cc: Ingo Molnar <mingo@kernel.org>
cc: "H. Peter Anvin" <hpa@zytor.com>
cc: x86@kernel.org
---
arch/x86/mm/testmmiotrace.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
index f6ae6830b341..bbaad357f5d7 100644
--- a/arch/x86/mm/testmmiotrace.c
+++ b/arch/x86/mm/testmmiotrace.c
@@ -115,6 +115,9 @@ static int __init init(void)
{
unsigned long size = (read_far) ? (8 << 20) : (16 << 10);
+ if (kernel_is_locked_down("MMIO trace testing"))
+ return -EPERM;
+
if (mmio_address == 0) {
pr_err("you have to use the module argument mmio_address.\n");
pr_err("DO NOT LOAD THIS MODULE UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!\n");
From patchwork Thu Oct 19 14:53:33 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [24/27] debugfs: Disallow use of debugfs files when the kernel is
locked down
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017379
Message-Id: <150842481363.7923.13021827051686067882.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:33 +0100
Disallow opening of debugfs files when the kernel is locked down as various
drivers give raw access to hardware through debugfs.
Accesses to tracefs should use /sys/kernel/tracing/ rather than
/sys/kernel/debug/tracing/. Possibly a symlink should be emplaced.
Normal device interaction should be done through configfs or a miscdev, not
debugfs.
Note that this makes it unnecessary to specifically lock down show_dsts(),
show_devs() and show_call() in the asus-wmi driver.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Andy Shevchenko <andy.shevchenko@gmail.com>
cc: acpi4asus-user@lists.sourceforge.net
cc: platform-driver-x86@vger.kernel.org
cc: Matthew Garrett <matthew.garrett@nebula.com>
cc: Thomas Gleixner <tglx@linutronix.de>
---
fs/debugfs/file.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 6dabc4a10396..32b5168a7e91 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -103,6 +103,9 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
const struct file_operations *real_fops = NULL;
int srcu_idx, r;
+ if (kernel_is_locked_down("debugfs"))
+ return -EPERM;
+
r = debugfs_use_file_start(dentry, &srcu_idx);
if (r) {
r = -ENOENT;
@@ -232,6 +235,9 @@ static int full_proxy_open(struct inode *inode, struct file *filp)
struct file_operations *proxy_fops = NULL;
int srcu_idx, r;
+ if (kernel_is_locked_down("debugfs"))
+ return -EPERM;
+
r = debugfs_use_file_start(dentry, &srcu_idx);
if (r) {
r = -ENOENT;
From patchwork Thu Oct 19 14:53:42 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [25/27] Lock down /proc/kcore
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017381
Message-Id: <150842482228.7923.9630520914833154257.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:42 +0100
Disallow access to /proc/kcore when the kernel is locked down to prevent
access to cryptographic data.
Signed-off-by: David Howells <dhowells@redhat.com>
---
fs/proc/kcore.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 45629f4b5402..176cf749e650 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -549,6 +549,8 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
static int open_kcore(struct inode *inode, struct file *filp)
{
+ if (kernel_is_locked_down("/proc/kcore"))
+ return -EPERM;
if (!capable(CAP_SYS_RAWIO))
return -EPERM;
From patchwork Thu Oct 19 14:53:51 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [26/27] efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017383
Message-Id: <150842483172.7923.2791223614506312745.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:51 +0100
UEFI machines can be booted in Secure Boot mode. Add an EFI_SECURE_BOOT
flag that can be passed to efi_enabled() to find out whether secure boot is
enabled.
Move the switch-statement in x86's setup_arch() that inteprets the
secure_boot boot parameter to generic code and set the bit there.
Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc: linux-efi@vger.kernel.org
---
arch/x86/kernel/setup.c | 14 +-------------
drivers/firmware/efi/Makefile | 1 +
drivers/firmware/efi/secureboot.c | 37 +++++++++++++++++++++++++++++++++++++
include/linux/efi.h | 16 ++++++++++------
4 files changed, 49 insertions(+), 19 deletions(-)
create mode 100644 drivers/firmware/efi/secureboot.c
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0957dd73d127..7c2162f9e769 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1197,19 +1197,7 @@ void __init setup_arch(char **cmdline_p)
/* Allocate bigger log buffer */
setup_log_buf(1);
- if (efi_enabled(EFI_BOOT)) {
- switch (boot_params.secure_boot) {
- case efi_secureboot_mode_disabled:
- pr_info("Secure boot disabled\n");
- break;
- case efi_secureboot_mode_enabled:
- pr_info("Secure boot enabled\n");
- break;
- default:
- pr_info("Secure boot could not be determined\n");
- break;
- }
- }
+ efi_set_secure_boot(boot_params.secure_boot);
reserve_initrd();
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 0329d319d89a..883f9f7eefc6 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -23,6 +23,7 @@ obj-$(CONFIG_EFI_FAKE_MEMMAP) += fake_mem.o
obj-$(CONFIG_EFI_BOOTLOADER_CONTROL) += efibc.o
obj-$(CONFIG_EFI_TEST) += test/
obj-$(CONFIG_EFI_DEV_PATH_PARSER) += dev-path-parser.o
+obj-$(CONFIG_EFI) += secureboot.o
obj-$(CONFIG_APPLE_PROPERTIES) += apple-properties.o
arm-obj-$(CONFIG_EFI) := arm-init.o arm-runtime.o
diff --git a/drivers/firmware/efi/secureboot.c b/drivers/firmware/efi/secureboot.c
new file mode 100644
index 000000000000..674dcc01bb0b
--- /dev/null
+++ b/drivers/firmware/efi/secureboot.c
@@ -0,0 +1,37 @@
+/* Core kernel secure boot support.
+ *
+ * Copyright (C) 2017 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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/efi.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+
+/*
+ * Decide what to do when UEFI secure boot mode is enabled.
+ */
+void __init efi_set_secure_boot(enum efi_secureboot_mode mode)
+{
+ if (efi_enabled(EFI_BOOT)) {
+ switch (mode) {
+ case efi_secureboot_mode_disabled:
+ 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:
+ pr_info("Secure boot could not be determined\n");
+ break;
+ }
+ }
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 66f4a4e79f4b..7c7a7e33e4d1 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1103,6 +1103,14 @@ 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? */
+
+enum efi_secureboot_mode {
+ efi_secureboot_mode_unset,
+ efi_secureboot_mode_unknown,
+ efi_secureboot_mode_disabled,
+ efi_secureboot_mode_enabled,
+};
#ifdef CONFIG_EFI
/*
@@ -1115,6 +1123,7 @@ static inline bool efi_enabled(int feature)
extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused);
extern bool efi_is_table_address(unsigned long phys_addr);
+extern void __init efi_set_secure_boot(enum efi_secureboot_mode mode);
#else
static inline bool efi_enabled(int feature)
{
@@ -1133,6 +1142,7 @@ static inline bool efi_is_table_address(unsigned long phys_addr)
{
return false;
}
+static inline void efi_set_secure_boot(enum efi_secureboot_mode mode) {}
#endif
extern int efi_status_to_err(efi_status_t status);
@@ -1518,12 +1528,6 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg,
bool efi_runtime_disabled(void);
extern void efi_call_virt_check_flags(unsigned long flags, const char *call);
-enum efi_secureboot_mode {
- efi_secureboot_mode_unset,
- efi_secureboot_mode_unknown,
- efi_secureboot_mode_disabled,
- efi_secureboot_mode_enabled,
-};
enum efi_secureboot_mode efi_get_secureboot(efi_system_table_t *sys_table);
#ifdef CONFIG_RESET_ATTACK_MITIGATION
From patchwork Thu Oct 19 14:53:59 2017
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [27/27] efi: Lock down the kernel if booted in secure boot mode
From: David Howells <dhowells@redhat.com>
X-Patchwork-Id: 10017385
Message-Id: <150842483945.7923.12778302394414653081.stgit@warthog.procyon.org.uk>
To: linux-security-module@vger.kernel.org
Cc: gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org,
matthew.garrett@nebula.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, dhowells@redhat.com, jforbes@redhat.com
Date: Thu, 19 Oct 2017 15:53:59 +0100
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>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc: linux-efi@vger.kernel.org
---
arch/x86/kernel/setup.c | 6 ++++--
security/Kconfig | 14 ++++++++++++++
security/lock_down.c | 1 +
3 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 7c2162f9e769..4e38327efb2e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -64,6 +64,7 @@
#include <linux/dma-mapping.h>
#include <linux/ctype.h>
#include <linux/uaccess.h>
+#include <linux/security.h>
#include <linux/percpu.h>
#include <linux/crash_dump.h>
@@ -1039,6 +1040,9 @@ void __init setup_arch(char **cmdline_p)
if (efi_enabled(EFI_BOOT))
efi_init();
+ efi_set_secure_boot(boot_params.secure_boot);
+ init_lockdown();
+
dmi_scan_machine();
dmi_memdev_walk();
dmi_set_dump_stack_arch_desc();
@@ -1197,8 +1201,6 @@ void __init setup_arch(char **cmdline_p)
/* Allocate bigger log buffer */
setup_log_buf(1);
- efi_set_secure_boot(boot_params.secure_boot);
-
reserve_initrd();
acpi_table_upgrade();
diff --git a/security/Kconfig b/security/Kconfig
index 4be6be71e075..e1756039dc0a 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -227,6 +227,20 @@ config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
combination on a wired keyboard.
+config LOCK_DOWN_IN_EFI_SECURE_BOOT
+ bool "Lock down the kernel in EFI Secure Boot mode"
+ default n
+ select LOCK_DOWN_KERNEL
+ depends on EFI
+ help
+ UEFI Secure Boot provides a mechanism for ensuring that the firmware
+ will only load signed bootloaders and kernels. Secure boot mode may
+ be determined from EFI variables provided by the system firmware if
+ not indicated by the boot parameters.
+
+ Enabling this option turns on results in kernel lockdown being
+ triggered if EFI Secure Boot is set.
+
source security/selinux/Kconfig
source security/smack/Kconfig
diff --git a/security/lock_down.c b/security/lock_down.c
index f71118c340d2..12c3bc204c4e 100644
--- a/security/lock_down.c
+++ b/security/lock_down.c
@@ -12,6 +12,7 @@
#include <linux/security.h>
#include <linux/export.h>
#include <linux/sysrq.h>
+#include <linux/efi.h>
#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT
static __read_mostly bool kernel_locked_down;