From c0f84a03f23b6d9beb72448e400c10e8071f999e Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Sun, 16 Feb 2020 21:13:31 +0000 Subject: [PATCH] [x86] Drop "Add a SysRq option to lift kernel lockdown" (Closes: #947021) - This patch allowed remotely disabling lockdown using usbip - Lockdown can be disabled by running "mokutil --disable-validation", rebooting, and confirming the change when prompted --- debian/changelog | 6 + ...SysRq-option-to-lift-kernel-lockdown.patch | 285 ------------------ debian/patches/series | 1 - 3 files changed, 6 insertions(+), 286 deletions(-) delete mode 100644 debian/patches/features/all/lockdown/0002-Add-a-SysRq-option-to-lift-kernel-lockdown.patch diff --git a/debian/changelog b/debian/changelog index 56857a32c..db345d4f2 100644 --- a/debian/changelog +++ b/debian/changelog @@ -5,6 +5,12 @@ linux (4.19.98-2) UNRELEASED; urgency=medium (CVE-2020-8428) * vfs: fix do_last() regression + [ Ben Hutchings ] + * [x86] Drop "Add a SysRq option to lift kernel lockdown" (Closes: #947021) + - This patch allowed remotely disabling lockdown using usbip + - Lockdown can be disabled by running "mokutil --disable-validation", + rebooting, and confirming the change when prompted + [ YunQiang Su ] * [mips*] enable CONFIG_MIPS_O32_FP64_SUPPORT. * [mips*] enable CONFIG_CPU_HAS_MSA except octeon. diff --git a/debian/patches/features/all/lockdown/0002-Add-a-SysRq-option-to-lift-kernel-lockdown.patch b/debian/patches/features/all/lockdown/0002-Add-a-SysRq-option-to-lift-kernel-lockdown.patch deleted file mode 100644 index faab06bcb..000000000 --- a/debian/patches/features/all/lockdown/0002-Add-a-SysRq-option-to-lift-kernel-lockdown.patch +++ /dev/null @@ -1,285 +0,0 @@ -From: Kyle McMartin -Date: Wed, 8 Nov 2017 15:11:31 +0000 -Subject: [02/29] Add a SysRq option to lift kernel lockdown -Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=47a04d29e952d4dd896f2ec4c2ecee6971ab364d - -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 -Signed-off-by: David Howells -cc: x86@kernel.org -[bwh: Forward-ported to 4.15] ---- - 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 | 10 ++++++++++ - security/lock_down.c | 47 ++++++++++++++++++++++++++++++++++++++++++++ - 8 files changed, 86 insertions(+), 8 deletions(-) - -Index: linux/arch/x86/include/asm/setup.h -=================================================================== ---- linux.orig/arch/x86/include/asm/setup.h -+++ linux/arch/x86/include/asm/setup.h -@@ -9,6 +9,8 @@ - #include - #include - -+#define LOCKDOWN_LIFT_KEY 'x' -+ - #ifdef __i386__ - - #include -Index: linux/drivers/input/misc/uinput.c -=================================================================== ---- linux.orig/drivers/input/misc/uinput.c -+++ linux/drivers/input/misc/uinput.c -@@ -366,6 +366,7 @@ static int uinput_create_device(struct u - dev->flush = uinput_dev_flush; - } - -+ dev->flags |= INPUTDEV_FLAGS_SYNTHETIC; - dev->event = uinput_dev_event; - - input_set_drvdata(udev->dev, udev); -Index: linux/drivers/tty/sysrq.c -=================================================================== ---- linux.orig/drivers/tty/sysrq.c -+++ linux/drivers/tty/sysrq.c -@@ -487,6 +487,7 @@ static struct sysrq_key_op *sysrq_key_ta - /* 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 */ -@@ -530,7 +531,7 @@ static void __sysrq_put_key_op(int key, - 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; -@@ -550,11 +551,15 @@ void __handle_sysrq(int key, bool check_ - - 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); -@@ -586,7 +591,7 @@ void __handle_sysrq(int key, bool check_ - void handle_sysrq(int key) - { - if (sysrq_on()) -- __handle_sysrq(key, true); -+ __handle_sysrq(key, SYSRQ_FROM_KERNEL); - } - EXPORT_SYMBOL(handle_sysrq); - -@@ -667,7 +672,7 @@ static void sysrq_do_reset(struct timer_ - 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 - - 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(struc - - if (get_user(c, buf)) - return -EFAULT; -- __handle_sysrq(c, false); -+ __handle_sysrq(c, SYSRQ_FROM_PROC); - } - - return count; -Index: linux/include/linux/input.h -=================================================================== ---- linux.orig/include/linux/input.h -+++ linux/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 - */ -Index: linux/include/linux/sysrq.h -=================================================================== ---- linux.orig/include/linux/sysrq.h -+++ linux/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); -Index: linux/kernel/debug/kdb/kdb_main.c -=================================================================== ---- linux.orig/kernel/debug/kdb/kdb_main.c -+++ linux/kernel/debug/kdb/kdb_main.c -@@ -1996,7 +1996,7 @@ static int kdb_sr(int argc, const char * - 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; -Index: linux/security/Kconfig -=================================================================== ---- linux.orig/security/Kconfig -+++ linux/security/Kconfig -@@ -247,6 +247,16 @@ 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_BY_SYSRQ -+ bool "Allow the kernel lockdown to be lifted by SysRq" -+ depends on LOCK_DOWN_KERNEL -+ depends on MAGIC_SYSRQ -+ depends on X86 -+ 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 -Index: linux/security/lock_down.c -=================================================================== ---- linux.orig/security/lock_down.c -+++ linux/security/lock_down.c -@@ -11,8 +11,14 @@ - - #include - #include -+#include -+#include - -+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ -+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 +64,44 @@ bool __kernel_is_locked_down(const char - return kernel_locked_down; - } - EXPORT_SYMBOL(__kernel_is_locked_down); -+ -+#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 = false; -+} -+ -+/* -+ * 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 */ diff --git a/debian/patches/series b/debian/patches/series index b4635a318..cbdf6f859 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -106,7 +106,6 @@ bugfix/all/rtc-s35390a-set-uie_unsupported.patch # Lockdown (formerly 'securelevel') patchset features/all/lockdown/0001-Add-the-ability-to-lock-down-access-to-the-running-k.patch -features/all/lockdown/0002-Add-a-SysRq-option-to-lift-kernel-lockdown.patch features/all/lockdown/0003-ima-require-secure_boot-rules-in-lockdown-mode.patch features/all/lockdown/0004-Enforce-module-signatures-if-the-kernel-is-locked-do.patch features/all/lockdown/0005-Restrict-dev-mem-kmem-port-when-the-kernel-is-locked.patch