diff options
Diffstat (limited to 'lift-lockdown-sysrq.patch')
| -rw-r--r-- | lift-lockdown-sysrq.patch | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/lift-lockdown-sysrq.patch b/lift-lockdown-sysrq.patch new file mode 100644 index 000000000..b465143fb --- /dev/null +++ b/lift-lockdown-sysrq.patch @@ -0,0 +1,287 @@ +From c2eb371cede78df9a47bf3a125aa9a45dd833da7 Mon Sep 17 00:00:00 2001 +From: Kyle McMartin <kyle@redhat.com> +Date: Mon, 9 Apr 2018 09:52:45 +0100 +Subject: [PATCH] Add a SysRq option to lift kernel lockdown + +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 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. +Since this macro must be defined in an arch to be able to use this facility +for that arch, the Kconfig option is restricted to arches that support it. + +Signed-off-by: Kyle McMartin <kyle@redhat.com> +Signed-off-by: David Howells <dhowells@redhat.com> +cc: x86@kernel.org +Signed-off-by: Jeremy Cline <jcline@redhat.com> +--- + arch/x86/include/asm/setup.h | 2 ++ + drivers/input/misc/uinput.c | 1 + + drivers/tty/sysrq.c | 27 +++++++++++++--------- + include/linux/input.h | 5 +++++ + include/linux/sysrq.h | 8 ++++++- + kernel/debug/kdb/kdb_main.c | 2 +- + security/lockdown/Kconfig | 11 +++++++++ + security/lockdown/lockdown.c | 43 ++++++++++++++++++++++++++++++++++++ + 8 files changed, 87 insertions(+), 12 deletions(-) + +diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h +index ed8ec011a9fd..8daf633a5347 100644 +--- a/arch/x86/include/asm/setup.h ++++ b/arch/x86/include/asm/setup.h +@@ -9,6 +9,8 @@ + #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 84051f20b18a..583ab2bc1916 100644 +--- a/drivers/input/misc/uinput.c ++++ b/drivers/input/misc/uinput.c +@@ -353,6 +353,7 @@ static int uinput_create_device(struct uinput_device *udev) + dev->flush = uinput_dev_flush; + } + ++ dev->flags |= INPUTDEV_FLAGS_SYNTHETIC; + dev->event = uinput_dev_event; + + input_set_drvdata(udev->dev, udev); +diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c +index 573b2055173c..99082faafc44 100644 +--- a/drivers/tty/sysrq.c ++++ b/drivers/tty/sysrq.c +@@ -480,6 +480,7 @@ 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 */ +@@ -523,7 +524,7 @@ 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; +@@ -546,11 +547,15 @@ void __handle_sysrq(int key, bool check_mask) + + op_p = __sysrq_get_key_op(key); + if (op_p) { +- /* +- * 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)) { ++ /* 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"); ++ } else if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) { ++ /* ++ * Should we check for enabled operations (/proc/sysrq-trigger ++ * should not) and is the invoked operation enabled? ++ */ + pr_info("%s\n", op_p->action_msg); + console_loglevel = orig_log_level; + op_p->handler(key); +@@ -585,7 +590,7 @@ 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); + +@@ -665,7 +670,7 @@ static void sysrq_do_reset(struct timer_list *t) + 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, +@@ -818,8 +823,10 @@ 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; + } +@@ -1102,7 +1109,7 @@ 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 94f277cd806a..8539afa2c001 100644 +--- a/include/linux/input.h ++++ b/include/linux/input.h +@@ -48,6 +48,7 @@ enum input_clock_type { + * @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.) +@@ -134,6 +135,8 @@ 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)]; +@@ -204,6 +207,8 @@ 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 8c71874e8485..7de1f08b60a9 100644 +--- a/include/linux/sysrq.h ++++ b/include/linux/sysrq.h +@@ -29,6 +29,8 @@ + #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; +@@ -43,8 +45,12 @@ 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 4567fe998c30..d05142ef44c4 100644 +--- a/kernel/debug/kdb/kdb_main.c ++++ b/kernel/debug/kdb/kdb_main.c +@@ -1981,7 +1981,7 @@ 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/lockdown/Kconfig b/security/lockdown/Kconfig +index e84ddf484010..20e979178e1c 100644 +--- a/security/lockdown/Kconfig ++++ b/security/lockdown/Kconfig +@@ -45,3 +45,14 @@ config LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY + disabled. + + endchoice ++ ++config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ ++ bool "Allow the kernel lockdown to be lifted by SysRq" ++ depends on SECURITY_LOCKDOWN_LSM ++ depends on !LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY ++ depends on !LOCK_DOWN_KERNEL_FORCE_INTEGRITY ++ depends on MAGIC_SYSRQ ++ depends on X86 ++ help ++ Allow setting the lockdown mode to "none" by pressing a SysRq key ++ combination on a wired keyboard. On x86, this is SysRq+x +diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c +index 8a10b43daf74..df4662257309 100644 +--- a/security/lockdown/lockdown.c ++++ b/security/lockdown/lockdown.c +@@ -13,6 +13,8 @@ + #include <linux/security.h> + #include <linux/export.h> + #include <linux/lsm_hooks.h> ++#include <linux/sysrq.h> ++#include <asm/setup.h> + + static enum lockdown_reason kernel_locked_down; + +@@ -179,6 +181,47 @@ static int __init lockdown_secfs_init(void) + return PTR_ERR_OR_ZERO(dentry); + } + ++#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ ++ ++/* ++ * Take the kernel out of lockdown mode. ++ */ ++static void lift_kernel_lockdown(void) ++{ ++ pr_notice("Lifting lockdown\n"); ++ kernel_locked_down = LOCKDOWN_NONE; ++} ++ ++/* ++ * Allow lockdown to be lifted by pressing something like SysRq+x (and not by ++ * echoing the appropriate letter into the sysrq-trigger file). ++ */ ++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_SYSRQ */ ++ + core_initcall(lockdown_secfs_init); + + #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY +-- +2.21.0 + |