Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/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 9d1f8be5cf42 ("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
  ...

1 files changed, 30 insertions, 7 deletions

diff --git a/kernel/module.c b/kernel/module.c
index edbe42755a27..ff2d7359a418 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2839,8 +2839,9 @@ static inline void kmemleak_load_module(const struct module *mod,
 #ifdef CONFIG_MODULE_SIG
 static int module_sig_check(struct load_info *info, int flags)
 {
-        int err = -ENOKEY;
+        int err = -ENODATA;
         const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+        const char *reason;
         const void *mod = info->hdr;
 
         /*
@@ -2855,16 +2856,38 @@ static int module_sig_check(struct load_info *info, int flags)
                 err = mod_verify_sig(mod, info);
         }
 
-        if (!err) {
+        switch (err) {
+        case 0:
                 info->sig_ok = true;
                 return 0;
-        }
 
-        /* Not having a signature is only an error if we're strict. */
-        if (err == -ENOKEY && !is_module_sig_enforced())
-                err = 0;
+                /* We don't permit modules to be loaded into trusted kernels
+                 * without a valid signature on them, but if we're not
+                 * enforcing, certain errors are non-fatal.
+                 */
+        case -ENODATA:
+                reason = "Loading of unsigned module";
+                goto decide;
+        case -ENOPKG:
+                reason = "Loading of module with unsupported crypto";
+                goto decide;
+        case -ENOKEY:
+                reason = "Loading of module with unavailable key";
+        decide:
+                if (is_module_sig_enforced()) {
+                        pr_notice("%s is rejected\n", reason);
+                        return -EKEYREJECTED;
+                }
 
-        return err;
+                return security_locked_down(LOCKDOWN_MODULE_SIGNATURE);
+
+                /* All other errors are fatal, including nomem, unparseable
+                 * signatures and signature check failures - even if signatures
+                 * aren't required.
+                 */
+        default:
+                return err;
+        }
 }
 #else /* !CONFIG_MODULE_SIG */
 static int module_sig_check(struct load_info *info, int flags)