Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/ke…

…rnel/git/jmorris/linux-security

Pull kernel lockdown mode from James Morris:
 "This is the latest iteration of the kernel lockdown patchset, from
  Matthew Garrett, David Howells and others.

  From the original description:

    This patchset introduces an optional kernel lockdown feature,
    intended to strengthen the boundary between UID 0 and the kernel.
    When enabled, various pieces of kernel functionality are restricted.
    Applications that rely on low-level access to either hardware or the
    kernel may cease working as a result - therefore this should not be
    enabled without appropriate evaluation beforehand.

    The majority of mainstream distributions have been carrying variants
    of this patchset for many years now, so there's value in providing a
    doesn't meet every distribution requirement, but gets us much closer
    to not requiring external patches.

  There are two major changes since this was last proposed for mainline:

   - Separating lockdown from EFI secure boot. Background discussion is
     covered here: https://lwn.net/Articles/751061/

   -  Implementation as an LSM, with a default stackable lockdown LSM
      module. This allows the lockdown feature to be policy-driven,
      rather than encoding an implicit policy within the mechanism.

  The new locked_down LSM hook is provided to allow LSMs to make a
  policy decision around whether kernel functionality that would allow
  tampering with or examining the runtime state of the kernel should be
  permitted.

  The included lockdown LSM provides an implementation with a simple
  policy intended for general purpose use. This policy provides a coarse
  level of granularity, controllable via the kernel command line:

    lockdown={integrity|confidentiality}

  Enable the kernel lockdown feature. If set to integrity, kernel features
  that allow userland to modify the running kernel are disabled. If set to
  confidentiality, kernel features that allow userland to extract
  confidential information from the kernel are also disabled.

  This may also be controlled via /sys/kernel/security/lockdown and
  overriden by kernel configuration.

  New or existing LSMs may implement finer-grained controls of the
  lockdown features. Refer to the lockdown_reason documentation in
  include/linux/security.h for details.

  The lockdown feature has had signficant design feedback and review
  across many subsystems. This code has been in linux-next for some
  weeks, with a few fixes applied along the way.

  Stephen Rothwell noted that commit 9d1f8be ("bpf: Restrict bpf
  when kernel lockdown is in confidentiality mode") is missing a
  Signed-off-by from its author. Matthew responded that he is providing
  this under category (c) of the DCO"

* 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (31 commits)
  kexec: Fix file verification on S390
  security: constify some arrays in lockdown LSM
  lockdown: Print current->comm in restriction messages
  efi: Restrict efivar_ssdt_load when the kernel is locked down
  tracefs: Restrict tracefs when the kernel is locked down
  debugfs: Restrict debugfs when the kernel is locked down
  kexec: Allow kexec_file() with appropriate IMA policy when locked down
  lockdown: Lock down perf when in confidentiality mode
  bpf: Restrict bpf when kernel lockdown is in confidentiality mode
  lockdown: Lock down tracing and perf kprobes when in confidentiality mode
  lockdown: Lock down /proc/kcore
  x86/mmiotrace: Lock down the testmmiotrace module
  lockdown: Lock down module params that specify hardware parameters (eg. ioport)
  lockdown: Lock down TIOCSSERIAL
  lockdown: Prohibit PCMCIA CIS storage when the kernel is locked down
  acpi: Disable ACPI table override if the kernel is locked down
  acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down
  ACPI: Limit access to custom_method when the kernel is locked down
  x86/msr: Restrict MSR access when the kernel is locked down
  x86: Lock down IO port access when the kernel is locked down
  ...

Documentation/admin-guide/kernel-parameters.txt

@@ -2276,6 +2276,15 @@
 	lockd.nlm_udpport=M	[NFS] Assign UDP port.
 			Format: <integer>
 
+	lockdown=	[SECURITY]
+			{ integrity | confidentiality }
+			Enable the kernel lockdown feature. If set to
+			integrity, kernel features that allow userland to
+			modify the running kernel are disabled. If set to
+			confidentiality, kernel features that allow userland
+			to extract confidential information from the kernel
+			are also disabled.
+
 	locktorture.nreaders_stress= [KNL]
 			Set the number of locking read-acquisition kthreads.
 			Defaults to being automatically set based on the

arch/arm64/Kconfig

@@ -982,7 +982,7 @@ config KEXEC_FILE
 	  for kernel and initramfs as opposed to list of segments as
 	  accepted by previous system call.
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE
 	help
@@ -997,13 +997,13 @@ config KEXEC_VERIFY_SIG
 config KEXEC_IMAGE_VERIFY_SIG
 	bool "Enable Image signature verification support"
 	default y
-	depends on KEXEC_VERIFY_SIG
+	depends on KEXEC_SIG
 	depends on EFI && SIGNED_PE_FILE_VERIFICATION
 	help
 	  Enable Image signature verification support.
 
 comment "Support for PE file signature verification disabled"
-	depends on KEXEC_VERIFY_SIG
+	depends on KEXEC_SIG
 	depends on !EFI || !SIGNED_PE_FILE_VERIFICATION
 
 config CRASH_DUMP

arch/s390/Kconfig

@@ -554,7 +554,7 @@ config ARCH_HAS_KEXEC_PURGATORY
 	def_bool y
 	depends on KEXEC_FILE
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE && MODULE_SIG_FORMAT
 	help

arch/s390/kernel/kexec_elf.c

@@ -130,7 +130,7 @@ static int s390_elf_probe(const char *buf, unsigned long len)
 const struct kexec_file_ops s390_kexec_elf_ops = {
 	.probe = s390_elf_probe,
 	.load = s390_elf_load,
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 	.verify_sig = s390_verify_sig,
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 };

arch/s390/kernel/kexec_image.c

@@ -59,7 +59,7 @@ static int s390_image_probe(const char *buf, unsigned long len)
 const struct kexec_file_ops s390_kexec_image_ops = {
 	.probe = s390_image_probe,
 	.load = s390_image_load,
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 	.verify_sig = s390_verify_sig,
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 };

arch/s390/kernel/machine_kexec_file.c

@@ -22,7 +22,7 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
 	NULL,
 };
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 {
 	const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
@@ -68,7 +68,7 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 				      VERIFYING_MODULE_SIGNATURE,
 				      NULL, NULL);
 }
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 
 static int kexec_file_update_purgatory(struct kimage *image,
 				       struct s390_load_data *data)

arch/x86/Kconfig

@@ -2031,20 +2031,30 @@ config KEXEC_FILE
 config ARCH_HAS_KEXEC_PURGATORY
 	def_bool KEXEC_FILE
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE
 	---help---
-	  This option makes kernel signature verification mandatory for
-	  the kexec_file_load() syscall.
 
-	  In addition to that option, you need to enable signature
+	  This option makes the kexec_file_load() syscall check for a valid
+	  signature of the kernel image.  The image can still be loaded without
+	  a valid signature unless you also enable KEXEC_SIG_FORCE, though if
+	  there's a signature that we can check, then it must be valid.
+
+	  In addition to this option, you need to enable signature
 	  verification for the corresponding kernel image type being
 	  loaded in order for this to work.
 
+config KEXEC_SIG_FORCE
+	bool "Require a valid signature in kexec_file_load() syscall"
+	depends on KEXEC_SIG
+	---help---
+	  This option makes kernel signature verification mandatory for
+	  the kexec_file_load() syscall.
+
 config KEXEC_BZIMAGE_VERIFY_SIG
 	bool "Enable bzImage signature verification support"
-	depends on KEXEC_VERIFY_SIG
+	depends on KEXEC_SIG
 	depends on SIGNED_PE_FILE_VERIFICATION
 	select SYSTEM_TRUSTED_KEYRING
 	---help---

arch/x86/boot/compressed/acpi.c

@@ -26,7 +26,7 @@ struct mem_vector immovable_mem[MAX_NUMNODES*2];
  */
 #define MAX_ADDR_LEN 19
 
-static acpi_physical_address get_acpi_rsdp(void)
+static acpi_physical_address get_cmdline_acpi_rsdp(void)
 {
 	acpi_physical_address addr = 0;
 
@@ -278,10 +278,7 @@ acpi_physical_address get_rsdp_addr(void)
 {
 	acpi_physical_address pa;
 
-	pa = get_acpi_rsdp();
-
-	if (!pa)
-		pa = boot_params->acpi_rsdp_addr;
+	pa = boot_params->acpi_rsdp_addr;
 
 	/*
 	 * Try to get EFI data from setup_data. This can happen when we're a
@@ -311,7 +308,17 @@ static unsigned long get_acpi_srat_table(void)
 	char arg[10];
 	u8 *entry;
 
-	rsdp = (struct acpi_table_rsdp *)(long)boot_params->acpi_rsdp_addr;
+	/*
+	 * Check whether we were given an RSDP on the command line. We don't
+	 * stash this in boot params because the kernel itself may have
+	 * different ideas about whether to trust a command-line parameter.
+	 */
+	rsdp = (struct acpi_table_rsdp *)get_cmdline_acpi_rsdp();
+
+	if (!rsdp)
+		rsdp = (struct acpi_table_rsdp *)(long)
+			boot_params->acpi_rsdp_addr;
+
 	if (!rsdp)
 		return 0;
 

arch/x86/include/asm/acpi.h

@@ -117,6 +117,12 @@ static inline bool acpi_has_cpu_in_madt(void)
 	return !!acpi_lapic;
 }
 
+#define ACPI_HAVE_ARCH_SET_ROOT_POINTER
+static inline void acpi_arch_set_root_pointer(u64 addr)
+{
+	x86_init.acpi.set_root_pointer(addr);
+}
+
 #define ACPI_HAVE_ARCH_GET_ROOT_POINTER
 static inline u64 acpi_arch_get_root_pointer(void)
 {
@@ -125,6 +131,7 @@ static inline u64 acpi_arch_get_root_pointer(void)
 
 void acpi_generic_reduced_hw_init(void);
 
+void x86_default_set_root_pointer(u64 addr);
 u64 x86_default_get_root_pointer(void);
 
 #else /* !CONFIG_ACPI */
@@ -138,6 +145,8 @@ static inline void disable_acpi(void) { }
 
 static inline void acpi_generic_reduced_hw_init(void) { }
 
+static inline void x86_default_set_root_pointer(u64 addr) { }
+
 static inline u64 x86_default_get_root_pointer(void)
 {
 	return 0;

arch/x86/include/asm/x86_init.h

@@ -134,10 +134,12 @@ struct x86_hyper_init {
 
 /**
  * struct x86_init_acpi - x86 ACPI init functions
+ * @set_root_poitner:		set RSDP address
  * @get_root_pointer:		get RSDP address
  * @reduced_hw_early_init:	hardware reduced platform early init
  */
 struct x86_init_acpi {
+	void (*set_root_pointer)(u64 addr);
 	u64 (*get_root_pointer)(void);
 	void (*reduced_hw_early_init)(void);
 };

arch/x86/kernel/acpi/boot.c

@@ -1760,6 +1760,11 @@ void __init arch_reserve_mem_area(acpi_physical_address addr, size_t size)
 	e820__update_table_print();
 }
 
+void x86_default_set_root_pointer(u64 addr)
+{
+	boot_params.acpi_rsdp_addr = addr;
+}
+
 u64 x86_default_get_root_pointer(void)
 {
 	return boot_params.acpi_rsdp_addr;

arch/x86/kernel/ima_arch.c

@@ -74,9 +74,9 @@ bool arch_ima_get_secureboot(void)
 
 /* secureboot arch rules */
 static const char * const sb_arch_rules[] = {
-#if !IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
+#if !IS_ENABLED(CONFIG_KEXEC_SIG)
 	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig",
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 	"measure func=KEXEC_KERNEL_CHECK",
 #if !IS_ENABLED(CONFIG_MODULE_SIG)
 	"appraise func=MODULE_CHECK appraise_type=imasig",

arch/x86/kernel/ioport.c

@@ -11,6 +11,7 @@
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/ioport.h>
+#include <linux/security.h>
 #include <linux/smp.h>
 #include <linux/stddef.h>
 #include <linux/slab.h>
@@ -31,7 +32,8 @@ long ksys_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) ||
+			security_locked_down(LOCKDOWN_IOPORT)))
 		return -EPERM;
 
 	/*
@@ -126,7 +128,8 @@ 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) ||
+		    security_locked_down(LOCKDOWN_IOPORT))
 			return -EPERM;
 	}
 	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |

arch/x86/kernel/kexec-bzimage64.c

@@ -180,6 +180,7 @@ 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;

arch/x86/kernel/msr.c

@@ -34,6 +34,7 @@
 #include <linux/notifier.h>
 #include <linux/uaccess.h>
 #include <linux/gfp.h>
+#include <linux/security.h>
 
 #include <asm/cpufeature.h>
 #include <asm/msr.h>
@@ -79,6 +80,10 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
 	int err = 0;
 	ssize_t bytes = 0;
 
+	err = security_locked_down(LOCKDOWN_MSR);
+	if (err)
+		return err;
+
 	if (count % 8)
 		return -EINVAL;	/* Invalid chunk size */
 
@@ -130,6 +135,9 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 			err = -EFAULT;
 			break;
 		}
+		err = security_locked_down(LOCKDOWN_MSR);
+		if (err)
+			break;
 		err = wrmsr_safe_regs_on_cpu(cpu, regs);
 		if (err)
 			break;

arch/x86/kernel/x86_init.c

@@ -95,6 +95,7 @@ struct x86_init_ops x86_init __initdata = {
 	},
 
 	.acpi = {
+		.set_root_pointer	= x86_default_set_root_pointer,
 		.get_root_pointer	= x86_default_get_root_pointer,
 		.reduced_hw_early_init	= acpi_generic_reduced_hw_init,
 	},

arch/x86/mm/testmmiotrace.c

@@ -8,6 +8,7 @@
 #include <linux/module.h>
 #include <linux/io.h>
 #include <linux/mmiotrace.h>
+#include <linux/security.h>
 
 static unsigned long mmio_address;
 module_param_hw(mmio_address, ulong, iomem, 0);
@@ -115,6 +116,10 @@ static void do_test_bulk_ioremapping(void)
 static int __init init(void)
 {
 	unsigned long size = (read_far) ? (8 << 20) : (16 << 10);
+	int ret = security_locked_down(LOCKDOWN_MMIOTRACE);
+
+	if (ret)
+		return ret;
 
 	if (mmio_address == 0) {
 		pr_err("you have to use the module argument mmio_address.\n");

crypto/asymmetric_keys/verify_pefile.c

@@ -96,7 +96,7 @@ static int pefile_parse_binary(const void *pebuf, unsigned int pelen,
 
 	if (!ddir->certs.virtual_address || !ddir->certs.size) {
 		pr_debug("Unsigned PE binary\n");
-		return -EKEYREJECTED;
+		return -ENODATA;
 	}
 
 	chkaddr(ctx->header_size, ddir->certs.virtual_address,
@@ -403,6 +403,8 @@ static int pefile_digest_pe(const void *pebuf, unsigned int pelen,
  *  (*) 0 if at least one signature chain intersects with the keys in the trust
  *	keyring, or:
  *
+ *  (*) -ENODATA if there is no signature present.
+ *
  *  (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
  *	chain.
  *

drivers/acpi/custom_method.c

@@ -9,6 +9,7 @@
 #include <linux/uaccess.h>
 #include <linux/debugfs.h>
 #include <linux/acpi.h>
+#include <linux/security.h>
 
 #include "internal.h"
 
@@ -29,6 +30,11 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 
 	struct acpi_table_header table;
 	acpi_status status;
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
+	if (ret)
+		return ret;
 
 	if (!(*ppos)) {
 		/* parse the table header to get the table length */

drivers/acpi/osl.c

@@ -27,6 +27,7 @@
 #include <linux/list.h>
 #include <linux/jiffies.h>
 #include <linux/semaphore.h>
+#include <linux/security.h>
 
 #include <asm/io.h>
 #include <linux/uaccess.h>
@@ -182,8 +183,19 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
 	acpi_physical_address pa;
 
 #ifdef CONFIG_KEXEC
-	if (acpi_rsdp)
+	/*
+	 * We may have been provided with an RSDP on the command line,
+	 * but if a malicious user has done so they may be pointing us
+	 * at modified ACPI tables that could alter kernel behaviour -
+	 * so, we check the lockdown status before making use of
+	 * it. If we trust it then also stash it in an architecture
+	 * specific location (if appropriate) so it can be carried
+	 * over further kexec()s.
+	 */
+	if (acpi_rsdp && !security_locked_down(LOCKDOWN_ACPI_TABLES)) {
+		acpi_arch_set_root_pointer(acpi_rsdp);
 		return acpi_rsdp;
+	}
 #endif
 	pa = acpi_arch_get_root_pointer();
 	if (pa)