[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
This commit is contained in:
parent
0283619ccb
commit
c0f84a03f2
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@ -5,6 +5,12 @@ linux (4.19.98-2) UNRELEASED; urgency=medium
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(CVE-2020-8428)
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* vfs: fix do_last() regression
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[ Ben Hutchings ]
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* [x86] Drop "Add a SysRq option to lift kernel lockdown" (Closes: #947021)
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- This patch allowed remotely disabling lockdown using usbip
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- Lockdown can be disabled by running "mokutil --disable-validation",
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rebooting, and confirming the change when prompted
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[ YunQiang Su ]
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* [mips*] enable CONFIG_MIPS_O32_FP64_SUPPORT.
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* [mips*] enable CONFIG_CPU_HAS_MSA except octeon.
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@ -1,285 +0,0 @@
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From: Kyle McMartin <kyle@redhat.com>
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Date: Wed, 8 Nov 2017 15:11:31 +0000
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Subject: [02/29] Add a SysRq option to lift kernel lockdown
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=47a04d29e952d4dd896f2ec4c2ecee6971ab364d
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Make an option to provide a sysrq key that will lift the kernel lockdown,
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thereby allowing the running kernel image to be accessed and modified.
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On x86 this is triggered with SysRq+x, but this key may not be available on
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all arches, so it is set by setting LOCKDOWN_LIFT_KEY in asm/setup.h.
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Since this macro must be defined in an arch to be able to use this facility
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for that arch, the Kconfig option is restricted to arches that support it.
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Signed-off-by: Kyle McMartin <kyle@redhat.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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cc: x86@kernel.org
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[bwh: Forward-ported to 4.15]
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---
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arch/x86/include/asm/setup.h | 2 ++
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drivers/input/misc/uinput.c | 1 +
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drivers/tty/sysrq.c | 19 ++++++++++++------
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include/linux/input.h | 5 +++++
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include/linux/sysrq.h | 8 +++++++-
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kernel/debug/kdb/kdb_main.c | 2 +-
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security/Kconfig | 10 ++++++++++
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security/lock_down.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
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8 files changed, 86 insertions(+), 8 deletions(-)
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Index: linux/arch/x86/include/asm/setup.h
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===================================================================
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--- linux.orig/arch/x86/include/asm/setup.h
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+++ linux/arch/x86/include/asm/setup.h
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@@ -9,6 +9,8 @@
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#include <linux/linkage.h>
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#include <asm/page_types.h>
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+#define LOCKDOWN_LIFT_KEY 'x'
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+
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#ifdef __i386__
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#include <linux/pfn.h>
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Index: linux/drivers/input/misc/uinput.c
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===================================================================
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--- linux.orig/drivers/input/misc/uinput.c
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+++ linux/drivers/input/misc/uinput.c
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@@ -366,6 +366,7 @@ static int uinput_create_device(struct u
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dev->flush = uinput_dev_flush;
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}
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+ dev->flags |= INPUTDEV_FLAGS_SYNTHETIC;
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dev->event = uinput_dev_event;
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input_set_drvdata(udev->dev, udev);
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Index: linux/drivers/tty/sysrq.c
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===================================================================
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--- linux.orig/drivers/tty/sysrq.c
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+++ linux/drivers/tty/sysrq.c
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@@ -487,6 +487,7 @@ static struct sysrq_key_op *sysrq_key_ta
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/* x: May be registered on mips for TLB dump */
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/* x: May be registered on ppc/powerpc for xmon */
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/* x: May be registered on sparc64 for global PMU dump */
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+ /* x: May be registered on x86_64 for disabling secure boot */
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NULL, /* x */
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/* y: May be registered on sparc64 for global register dump */
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NULL, /* y */
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@@ -530,7 +531,7 @@ static void __sysrq_put_key_op(int key,
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sysrq_key_table[i] = op_p;
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}
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-void __handle_sysrq(int key, bool check_mask)
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+void __handle_sysrq(int key, unsigned int from)
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{
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struct sysrq_key_op *op_p;
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int orig_log_level;
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@@ -550,11 +551,15 @@ void __handle_sysrq(int key, bool check_
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op_p = __sysrq_get_key_op(key);
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if (op_p) {
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+ /* Ban synthetic events from some sysrq functionality */
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+ if ((from == SYSRQ_FROM_PROC || from == SYSRQ_FROM_SYNTHETIC) &&
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+ op_p->enable_mask & SYSRQ_DISABLE_USERSPACE)
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+ printk("This sysrq operation is disabled from userspace.\n");
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/*
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* Should we check for enabled operations (/proc/sysrq-trigger
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* should not) and is the invoked operation enabled?
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*/
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- if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
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+ if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) {
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pr_cont("%s\n", op_p->action_msg);
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console_loglevel = orig_log_level;
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op_p->handler(key);
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@@ -586,7 +591,7 @@ void __handle_sysrq(int key, bool check_
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void handle_sysrq(int key)
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{
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if (sysrq_on())
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- __handle_sysrq(key, true);
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+ __handle_sysrq(key, SYSRQ_FROM_KERNEL);
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}
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EXPORT_SYMBOL(handle_sysrq);
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@@ -667,7 +672,7 @@ static void sysrq_do_reset(struct timer_
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static void sysrq_handle_reset_request(struct sysrq_state *state)
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{
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if (state->reset_requested)
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- __handle_sysrq(sysrq_xlate[KEY_B], false);
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+ __handle_sysrq(sysrq_xlate[KEY_B], SYSRQ_FROM_KERNEL);
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if (sysrq_reset_downtime_ms)
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mod_timer(&state->keyreset_timer,
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@@ -818,8 +823,10 @@ static bool sysrq_handle_keypress(struct
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default:
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if (sysrq->active && value && value != 2) {
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+ int from = sysrq->handle.dev->flags & INPUTDEV_FLAGS_SYNTHETIC ?
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+ SYSRQ_FROM_SYNTHETIC : 0;
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sysrq->need_reinject = false;
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- __handle_sysrq(sysrq_xlate[code], true);
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+ __handle_sysrq(sysrq_xlate[code], from);
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}
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break;
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}
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@@ -1102,7 +1109,7 @@ static ssize_t write_sysrq_trigger(struc
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if (get_user(c, buf))
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return -EFAULT;
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- __handle_sysrq(c, false);
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+ __handle_sysrq(c, SYSRQ_FROM_PROC);
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}
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return count;
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Index: linux/include/linux/input.h
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===================================================================
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--- linux.orig/include/linux/input.h
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+++ linux/include/linux/input.h
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@@ -42,6 +42,7 @@ struct input_value {
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* @phys: physical path to the device in the system hierarchy
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* @uniq: unique identification code for the device (if device has it)
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* @id: id of the device (struct input_id)
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+ * @flags: input device flags (SYNTHETIC, etc.)
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* @propbit: bitmap of device properties and quirks
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* @evbit: bitmap of types of events supported by the device (EV_KEY,
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* EV_REL, etc.)
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@@ -124,6 +125,8 @@ struct input_dev {
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const char *uniq;
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struct input_id id;
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+ unsigned int flags;
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+
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unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];
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unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
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@@ -190,6 +193,8 @@ struct input_dev {
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};
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#define to_input_dev(d) container_of(d, struct input_dev, dev)
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+#define INPUTDEV_FLAGS_SYNTHETIC 0x000000001
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+
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/*
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* Verify that we are in sync with input_device_id mod_devicetable.h #defines
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*/
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Index: linux/include/linux/sysrq.h
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===================================================================
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--- linux.orig/include/linux/sysrq.h
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+++ linux/include/linux/sysrq.h
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@@ -29,6 +29,8 @@
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#define SYSRQ_ENABLE_BOOT 0x0080
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#define SYSRQ_ENABLE_RTNICE 0x0100
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+#define SYSRQ_DISABLE_USERSPACE 0x00010000
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+
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struct sysrq_key_op {
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void (*handler)(int);
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char *help_msg;
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@@ -43,8 +45,12 @@ struct sysrq_key_op {
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* are available -- else NULL's).
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*/
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+#define SYSRQ_FROM_KERNEL 0x0001
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+#define SYSRQ_FROM_PROC 0x0002
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+#define SYSRQ_FROM_SYNTHETIC 0x0004
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+
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void handle_sysrq(int key);
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-void __handle_sysrq(int key, bool check_mask);
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+void __handle_sysrq(int key, unsigned int from);
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int register_sysrq_key(int key, struct sysrq_key_op *op);
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int unregister_sysrq_key(int key, struct sysrq_key_op *op);
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struct sysrq_key_op *__sysrq_get_key_op(int key);
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Index: linux/kernel/debug/kdb/kdb_main.c
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===================================================================
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--- linux.orig/kernel/debug/kdb/kdb_main.c
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+++ linux/kernel/debug/kdb/kdb_main.c
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@@ -1996,7 +1996,7 @@ static int kdb_sr(int argc, const char *
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return KDB_ARGCOUNT;
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kdb_trap_printk++;
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- __handle_sysrq(*argv[1], check_mask);
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+ __handle_sysrq(*argv[1], check_mask ? SYSRQ_FROM_KERNEL : 0);
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kdb_trap_printk--;
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return 0;
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Index: linux/security/Kconfig
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===================================================================
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--- linux.orig/security/Kconfig
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+++ linux/security/Kconfig
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@@ -247,6 +247,16 @@ config LOCK_DOWN_KERNEL
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turns off various features that might otherwise allow access to the
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kernel image (eg. setting MSR registers).
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+config ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
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+ bool "Allow the kernel lockdown to be lifted by SysRq"
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+ depends on LOCK_DOWN_KERNEL
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+ depends on MAGIC_SYSRQ
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+ depends on X86
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+ help
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+ Allow the lockdown on a kernel to be lifted, by pressing a SysRq key
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+ combination on a wired keyboard.
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+
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+
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source security/selinux/Kconfig
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source security/smack/Kconfig
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source security/tomoyo/Kconfig
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Index: linux/security/lock_down.c
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===================================================================
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--- linux.orig/security/lock_down.c
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+++ linux/security/lock_down.c
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@@ -11,8 +11,14 @@
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#include <linux/security.h>
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#include <linux/export.h>
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+#include <linux/sysrq.h>
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+#include <asm/setup.h>
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+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
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+static __read_mostly bool kernel_locked_down;
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+#else
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static __ro_after_init bool kernel_locked_down;
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+#endif
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/*
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* Put the kernel into lock-down mode.
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@@ -58,3 +64,44 @@ bool __kernel_is_locked_down(const char
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return kernel_locked_down;
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}
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EXPORT_SYMBOL(__kernel_is_locked_down);
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+
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+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ
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+
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+/*
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+ * Take the kernel out of lockdown mode.
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+ */
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+static void lift_kernel_lockdown(void)
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+{
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+ pr_notice("Lifting lockdown\n");
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+ kernel_locked_down = false;
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+}
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+
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+/*
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+ * Allow lockdown to be lifted by pressing something like SysRq+x (and not by
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+ * echoing the appropriate letter into the sysrq-trigger file).
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+ */
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+static void sysrq_handle_lockdown_lift(int key)
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+{
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+ if (kernel_locked_down)
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+ lift_kernel_lockdown();
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+}
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+
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+static struct sysrq_key_op lockdown_lift_sysrq_op = {
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+ .handler = sysrq_handle_lockdown_lift,
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+ .help_msg = "unSB(x)",
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+ .action_msg = "Disabling Secure Boot restrictions",
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+ .enable_mask = SYSRQ_DISABLE_USERSPACE,
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+};
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+
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+static int __init lockdown_lift_sysrq(void)
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+{
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+ if (kernel_locked_down) {
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+ lockdown_lift_sysrq_op.help_msg[5] = LOCKDOWN_LIFT_KEY;
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+ register_sysrq_key(LOCKDOWN_LIFT_KEY, &lockdown_lift_sysrq_op);
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+ }
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+ return 0;
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+}
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+
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+late_initcall(lockdown_lift_sysrq);
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+
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+#endif /* CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ */
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@ -106,7 +106,6 @@ bugfix/all/rtc-s35390a-set-uie_unsupported.patch
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# Lockdown (formerly 'securelevel') patchset
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features/all/lockdown/0001-Add-the-ability-to-lock-down-access-to-the-running-k.patch
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features/all/lockdown/0002-Add-a-SysRq-option-to-lift-kernel-lockdown.patch
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features/all/lockdown/0003-ima-require-secure_boot-rules-in-lockdown-mode.patch
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features/all/lockdown/0004-Enforce-module-signatures-if-the-kernel-is-locked-do.patch
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features/all/lockdown/0005-Restrict-dev-mem-kmem-port-when-the-kernel-is-locked.patch
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