Revert "UBUNTU: SAUCE: (efi-lockdown) Add a SysRq option to lift kernel lockdown"

BugLink: https://bugs.launchpad.net/bugs/1861238
This reverts commit 531c25a35b2a93e025e72e04f16b0f3620ace581.

The original intent behind Lockdown's SysRq support was that the SysRq
command to lift Lockdown would only be honored if the command was
physically entered on a keyboard. Attempts to synthetically generate the
SysRq command, by a software program, were to be ignored since software,
even running as root, must not have the authorization to lift Lockdown.

Unfortunately, attempts to detect a synthetic SysRq command can be
thwarted by a privileged process that is able to set up a USB/IP
connection as the USB/IP connection could be used to lift Lockdown.

Remove the ability to lift Lockdown using SysRq.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Sultan Alsawaf <sultan.alsawaf@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index 3108e297d87d1bd4332bd18d8dbb1bef0c8ead45..ae13bc974416fd8483f822684165de310933f407 100644 (file)
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -9,8 +9,6 @@
 #include <linux/linkage.h>
 #include <asm/page_types.h>
 
-#define LOCKDOWN_LIFT_KEY 'x'
-
 #ifdef __i386__
 
 #include <linux/pfn.h>

diff --git a/debian.master/config/amd64/config.common.amd64 b/debian.master/config/amd64/config.common.amd64
index 7cd187de7d8a1ccaaba9804b05d9a52b6d724f9d..ed3d99b58abe3a43c04275a58beebe80d2e1af78 100644 (file)
--- a/debian.master/config/amd64/config.common.amd64
+++ b/debian.master/config/amd64/config.common.amd64
@@ -12,7 +12,6 @@ CONFIG_ADFS_FS=m
 CONFIG_AFFS_FS=m
 CONFIG_AIX_PARTITION=y
 CONFIG_ALIM7101_WDT=m
-CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ=y
 CONFIG_ALTERA_TSE=m
 CONFIG_AMD_XGBE_HAVE_ECC=y
 CONFIG_AMIGA_PARTITION=y

diff --git a/debian.master/config/annotations b/debian.master/config/annotations
index 7eee1d1588af16f49fbc9fe77f2bcba12ef0475a..d4ba76f3a3505abec37473695f78fddf521dbbc5 100644 (file)
--- a/debian.master/config/annotations
+++ b/debian.master/config/annotations
@@ -11518,11 +11518,9 @@ CONFIG_HARDENED_USERCOPY_PAGESPAN               policy<{'amd64': 'n', 'arm64': '
 CONFIG_FORTIFY_SOURCE                           policy<{'amd64': 'y', 'arm64': 'y', 'i386': 'y', 'ppc64el': 'y', 's390x': 'y'}>
 CONFIG_STATIC_USERMODEHELPER                    policy<{'amd64': 'n', 'arm64': 'n', 'armhf': 'n', 'i386': 'n', 'ppc64el': 'n', 's390x': 'n'}>
 CONFIG_LOCK_DOWN_KERNEL                         policy<{'amd64': 'y', 'arm64': 'y', 'armhf': 'y', 'i386': 'y', 'ppc64el': 'n', 's390x': 'n'}>
-CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ             policy<{'amd64': 'y', 'arm64': 'n', 'armhf': 'n', 'i386': 'y'}>
 CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT             policy<{'amd64': 'y', 'arm64': 'y', 'armhf': 'y', 'i386': 'y'}>
 #
 CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT             mark<ENFORCED>
-CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ             mark<ENFORCED>
 CONFIG_LOCK_DOWN_KERNEL                         mark<ENFORCED> flag<REVIEW>
 
 # Menu: Security options >> Default security module

diff --git a/debian.master/config/arm64/config.common.arm64 b/debian.master/config/arm64/config.common.arm64
index e9ab42f9c080a260a51281a08552a723190f9480..ff094a2408a407c93e4ec5c695a0027ee23536a2 100644 (file)
--- a/debian.master/config/arm64/config.common.arm64
+++ b/debian.master/config/arm64/config.common.arm64
@@ -12,7 +12,6 @@ CONFIG_ADFS_FS=m
 CONFIG_AFFS_FS=m
 CONFIG_AIX_PARTITION=y
 CONFIG_ALIM7101_WDT=m
-# CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ is not set
 CONFIG_ALTERA_TSE=m
 # CONFIG_AMD_XGBE_HAVE_ECC is not set
 CONFIG_AMIGA_PARTITION=y

diff --git a/debian.master/config/armhf/config.common.armhf b/debian.master/config/armhf/config.common.armhf
index 5c6fb4a6963116fad7beb5e16277ae4a2b5a4e25..83e558265e83fa29f8d23ae82af0fbc27c383de4 100644 (file)
--- a/debian.master/config/armhf/config.common.armhf
+++ b/debian.master/config/armhf/config.common.armhf
@@ -8,7 +8,6 @@ CONFIG_ADFS_FS=m
 CONFIG_AFFS_FS=m
 CONFIG_AIX_PARTITION=y
 CONFIG_ALIM7101_WDT=m
-# CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ is not set
 CONFIG_ALTERA_TSE=m
 # CONFIG_AMD_XGBE_HAVE_ECC is not set
 CONFIG_AMIGA_PARTITION=y

diff --git a/debian.master/config/i386/config.common.i386 b/debian.master/config/i386/config.common.i386
index b93051b26b4317b108a4c1c8acde060c9bba47ac..d002cb217ce62539e0baf7a358174a74aa732479 100644 (file)
--- a/debian.master/config/i386/config.common.i386
+++ b/debian.master/config/i386/config.common.i386
@@ -12,7 +12,6 @@ CONFIG_ADFS_FS=m
 CONFIG_AFFS_FS=m
 CONFIG_AIX_PARTITION=y
 CONFIG_ALIM7101_WDT=m
-CONFIG_ALLOW_LOCKDOWN_LIFT_BY_SYSRQ=y
 CONFIG_ALTERA_TSE=m
 CONFIG_AMD_XGBE_HAVE_ECC=y
 CONFIG_AMIGA_PARTITION=y

diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 79dc351ce53cfc80ffd6cd263507847ff7e3616b..4d0268efa2caded57d2b435d839b800593cf44b5 100644 (file)
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -363,7 +363,6 @@ 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 f7200393771727c27088695f53183d1c1dee2621..b674793be478442874a7ca62de1aeccc8ae3c50e 100644 (file)
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -487,7 +487,6 @@ 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 */
@@ -531,7 +530,7 @@ 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, unsigned int from)
+void __handle_sysrq(int key, bool check_mask)
 {
        struct sysrq_key_op *op_p;
        int orig_log_level;
@@ -551,15 +550,11 @@ void __handle_sysrq(int key, unsigned int from)
 
         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");
-               } 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?
-                        */
+               /*
+                * 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)) {
                        pr_cont("%s\n", op_p->action_msg);
                        console_loglevel = orig_log_level;
                        op_p->handler(key);
@@ -591,7 +586,7 @@ void __handle_sysrq(int key, unsigned int from)
 void handle_sysrq(int key)
 {
        if (sysrq_on())
-               __handle_sysrq(key, SYSRQ_FROM_KERNEL);
+               __handle_sysrq(key, true);
 }
 EXPORT_SYMBOL(handle_sysrq);
 
@@ -672,7 +667,7 @@ 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], SYSRQ_FROM_KERNEL);
+               __handle_sysrq(sysrq_xlate[KEY_B], false);
 
        if (sysrq_reset_downtime_ms)
                mod_timer(&state->keyreset_timer,
@@ -823,10 +818,8 @@ 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], from);
+                       __handle_sysrq(sysrq_xlate[code], true);
                }
                break;
        }
@@ -1109,7 +1102,7 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 
                if (get_user(c, buf))
                        return -EFAULT;
-               __handle_sysrq(c, SYSRQ_FROM_PROC);
+               __handle_sysrq(c, false);
        }
 
        return count;

diff --git a/include/linux/input.h b/include/linux/input.h
index 38cd0ea72c376e0363f05e73683b2bea2d1a99fa..7c7516eb7d76c64071e51c199fdb0fd0f4e3c934 100644 (file)
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -42,7 +42,6 @@ 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.)
@@ -125,8 +124,6 @@ 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)];
@@ -193,8 +190,6 @@ 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 7de1f08b60a913dc1cf06fe86c3132982c6db8a8..8c71874e84852b5cefb9b9bf0a06a877457eaf86 100644 (file)
--- a/include/linux/sysrq.h
+++ b/include/linux/sysrq.h
@@ -29,8 +29,6 @@
 #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;
@@ -45,12 +43,8 @@ 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, unsigned int from);
+void __handle_sysrq(int key, bool check_mask);
 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 10a11b82701c4286b615ddb3745daa845d52a3c0..15d902daeef6c97574c14652692f40202d9c02f9 100644 (file)
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1985,7 +1985,7 @@ static int kdb_sr(int argc, const char **argv)
                return KDB_ARGCOUNT;
 
        kdb_trap_printk++;
-       __handle_sysrq(*argv[1], check_mask ? SYSRQ_FROM_KERNEL : 0);
+       __handle_sysrq(*argv[1], check_mask);
        kdb_trap_printk--;
 
        return 0;

diff --git a/security/Kconfig b/security/Kconfig
index ffe994d38c23f4ee1dd0319da4900ec01a9c4544..103cb39baed2ed59ef131dd5afe7330fa8aa711b 100644 (file)
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -267,13 +267,6 @@ 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 && MAGIC_SYSRQ
-       help
-         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

diff --git a/security/lock_down.c b/security/lock_down.c
index 527f7e51dc8de092d33be4085cbfbc6193129a29..0e2ffa4c8fbfdd2b12b3867b3a7bfd25e16dd5ec 100644 (file)
--- a/security/lock_down.c
+++ b/security/lock_down.c
@@ -11,15 +11,9 @@
 
 #include <linux/security.h>
 #include <linux/export.h>
-#include <linux/sysrq.h>
 #include <linux/efi.h>
-#include <asm/setup.h>
 
-#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.
@@ -65,44 +59,3 @@ bool __kernel_is_locked_down(const char *what, bool first)
        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 */