-# Kconfig hardened check
+# kconfig-hardened-check
+
+![functional test](https://github.com/a13xp0p0v/kconfig-hardened-check/workflows/functional%20test/badge.svg)
+[![Coverage Status](https://codecov.io/gh/a13xp0p0v/kconfig-hardened-check/graph/badge.svg)](https://codecov.io/gh/a13xp0p0v/kconfig-hardened-check)
## Motivation
But nobody likes checking configs manually. So let the computers do their job!
__kconfig-hardened-check.py__ helps me to check the Linux kernel Kconfig option list
-against my hardening preferences for `x86_64`, which are based on the
-[KSPP recommended settings][1]
+against my hardening preferences, which are based on the
+
+ - [KSPP recommended settings][1],
+ - [CLIP OS kernel configuration][2],
+ - last public [grsecurity][3] patch (options which they disable),
+ - [SECURITY_LOCKDOWN_LSM][5] patchset,
+ - direct feedback from Linux kernel maintainers (Daniel Vetter in [issue #38][6]).
+
+I also created [__Linux Kernel Defence Map__][4] that is a graphical representation of the
+relationships between these hardening features and the corresponding vulnerability classes
+or exploitation techniques.
+
+## Supported microarchitectures
+
+ - X86_64
+ - X86_32
+ - ARM64
+ - ARM
-Please don't cry if my Python code looks like C. I'm just a kernel developer.
+## Installation
-## Script output examples
+You can install the package:
-### Usage
```
-#./kconfig-hardened-check.py
-Usage: ./kconfig-hardened-check.py [-p | -c <config_file>]
- -p, --print
- print hardening preferences
- -c <config_file>, --config=<config_file>
- check the config_file against these preferences
+pip install git+https://github.com/a13xp0p0v/kconfig-hardened-check
```
-### Script output for `Ubuntu 18.04 (Bionic Beaver)` kernel config
+or simply run `./bin/kconfig-hardened-check` from the cloned repository.
+
+## Usage
```
-./kconfig-hardened-check.py -c ubuntu-bionic-generic.config
-[+] Checking "ubuntu-bionic-generic.config" against hardening preferences...
- option name | desired val | decision | reason || check result
- ===========================================================================================================
- CONFIG_BUG | y | ubuntu18 | self_protection || OK
- CONFIG_PAGE_TABLE_ISOLATION | y | ubuntu18 | self_protection || OK
- CONFIG_RETPOLINE | y | ubuntu18 | self_protection || OK
- CONFIG_X86_64 | y | ubuntu18 | self_protection || OK
- CONFIG_STRICT_KERNEL_RWX | y | ubuntu18 | self_protection || OK
- CONFIG_STRICT_MODULE_RWX | y | ubuntu18 | self_protection || OK
- CONFIG_DEBUG_WX | y | ubuntu18 | self_protection || OK
- CONFIG_RANDOMIZE_BASE | y | ubuntu18 | self_protection || OK
- CONFIG_RANDOMIZE_MEMORY | y | ubuntu18 | self_protection || OK
- CONFIG_CC_STACKPROTECTOR_STRONG | y | ubuntu18 | self_protection || OK
- CONFIG_VMAP_STACK | y | ubuntu18 | self_protection || OK
- CONFIG_THREAD_INFO_IN_TASK | y | ubuntu18 | self_protection || OK
- CONFIG_SCHED_STACK_END_CHECK | y | ubuntu18 | self_protection || OK
- CONFIG_SLUB_DEBUG | y | ubuntu18 | self_protection || OK
- CONFIG_SLAB_FREELIST_HARDENED | y | ubuntu18 | self_protection || OK
- CONFIG_SLAB_FREELIST_RANDOM | y | ubuntu18 | self_protection || OK
- CONFIG_HARDENED_USERCOPY | y | ubuntu18 | self_protection || OK
- CONFIG_FORTIFY_SOURCE | y | ubuntu18 | self_protection || OK
- CONFIG_STRICT_DEVMEM | y | ubuntu18 | self_protection || OK
- CONFIG_SYN_COOKIES | y | ubuntu18 | self_protection || OK
- CONFIG_SECCOMP | y | ubuntu18 | self_protection || OK
- CONFIG_SECCOMP_FILTER | y | ubuntu18 | self_protection || OK
- CONFIG_MODULE_SIG | y | ubuntu18 | self_protection || OK
- CONFIG_MODULE_SIG_ALL | y | ubuntu18 | self_protection || OK
- CONFIG_MODULE_SIG_SHA512 | y | ubuntu18 | self_protection || OK
- CONFIG_DEFAULT_MMAP_MIN_ADDR | 65536 | ubuntu18 | self_protection || OK
- CONFIG_BUG_ON_DATA_CORRUPTION | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_PAGE_POISONING | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_GCC_PLUGINS | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_GCC_PLUGIN_RANDSTRUCT | y | kspp | self_protection || FAIL: not found
- CONFIG_GCC_PLUGIN_STRUCTLEAK | y | kspp | self_protection || FAIL: not found
- CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL | y | kspp | self_protection || FAIL: not found
- CONFIG_GCC_PLUGIN_LATENT_ENTROPY | y | kspp | self_protection || FAIL: not found
- CONFIG_IO_STRICT_DEVMEM | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_REFCOUNT_FULL | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_DEBUG_LIST | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_DEBUG_SG | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_DEBUG_CREDENTIALS | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_DEBUG_NOTIFIERS | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_MODULE_SIG_FORCE | y | kspp | self_protection || FAIL: "is not set"
- CONFIG_HARDENED_USERCOPY_FALLBACK | is not set | kspp | self_protection || FAIL: not found
- CONFIG_GCC_PLUGIN_STACKLEAK | y | my | self_protection || FAIL: not found
- CONFIG_SLUB_DEBUG_ON | y | my | self_protection || FAIL: "is not set"
- CONFIG_SECURITY_DMESG_RESTRICT | y | my | self_protection || FAIL: "is not set"
- CONFIG_STATIC_USERMODEHELPER | y | my | self_protection || FAIL: "is not set"
- CONFIG_SECURITY | y | ubuntu18 | security_policy || OK
- CONFIG_SECURITY_YAMA | y | ubuntu18 | security_policy || OK
- CONFIG_SECURITY_SELINUX_DISABLE | is not set | ubuntu18 | security_policy || OK
- CONFIG_ACPI_CUSTOM_METHOD | is not set | ubuntu18 | cut_attack_surface || OK
- CONFIG_COMPAT_BRK | is not set | ubuntu18 | cut_attack_surface || OK
- CONFIG_DEVKMEM | is not set | ubuntu18 | cut_attack_surface || OK
- CONFIG_COMPAT_VDSO | is not set | ubuntu18 | cut_attack_surface || OK
- CONFIG_LEGACY_VSYSCALL_NONE | y | kspp | cut_attack_surface || FAIL: "is not set"
- CONFIG_BINFMT_MISC | is not set | kspp | cut_attack_surface || FAIL: "m"
- CONFIG_INET_DIAG | is not set | kspp | cut_attack_surface || FAIL: "m"
- CONFIG_KEXEC | is not set | kspp | cut_attack_surface || FAIL: "y"
- CONFIG_PROC_KCORE | is not set | kspp | cut_attack_surface || FAIL: "y"
- CONFIG_LEGACY_PTYS | is not set | kspp | cut_attack_surface || FAIL: "y"
- CONFIG_IA32_EMULATION | is not set | kspp | cut_attack_surface || FAIL: "y"
- CONFIG_X86_X32 | is not set | kspp | cut_attack_surface || FAIL: "y"
- CONFIG_MODIFY_LDT_SYSCALL | is not set | kspp | cut_attack_surface || FAIL: "y"
- CONFIG_KEXEC_FILE | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_LIVEPATCH | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_USER_NS | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_IP_DCCP | is not set | my | cut_attack_surface || FAIL: "m"
- CONFIG_IP_SCTP | is not set | my | cut_attack_surface || FAIL: "m"
- CONFIG_FTRACE | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_KPROBES | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_PROFILING | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_UPROBES | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_BPF_JIT | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_BPF_SYSCALL | is not set | my | cut_attack_surface || FAIL: "y"
- CONFIG_LKDTM | m | my | feature_test || FAIL: "is not set"
-
-[-] config check is NOT PASSED: 40 errors
+usage: kconfig-hardened-check [-h] [--version] [-p {X86_64,X86_32,ARM64,ARM}]
+ [-c CONFIG]
+ [-m {verbose,json,show_ok,show_fail}]
+
+Checks the hardening options in the Linux kernel config
+
+optional arguments:
+ -h, --help show this help message and exit
+ --version show program's version number and exit
+ -p {X86_64,X86_32,ARM64,ARM}, --print {X86_64,X86_32,ARM64,ARM}
+ print hardening preferences for selected architecture
+ -c CONFIG, --config CONFIG
+ check the kernel config file against these preferences
+ -m {verbose,json,show_ok,show_fail}, --mode {verbose,json,show_ok,show_fail}
+ choose the report mode
```
-__Go and fix them all!__
+## Output for `Ubuntu 20.04 LTS (Focal Fossa)` kernel config
+```
+$ ./bin/kconfig-hardened-check -c kconfig_hardened_check/config_files/distros/ubuntu-focal.config
+[+] Config file to check: kconfig_hardened_check/config_files/distros/ubuntu-focal.config
+[+] Detected architecture: X86_64
+[+] Detected kernel version: 5.4
+=========================================================================================================================
+ option name | desired val | decision | reason | check result
+=========================================================================================================================
+CONFIG_BUG | y |defconfig | self_protection | OK
+CONFIG_SLUB_DEBUG | y |defconfig | self_protection | OK
+CONFIG_GCC_PLUGINS | y |defconfig | self_protection | FAIL: not found
+CONFIG_STACKPROTECTOR_STRONG | y |defconfig | self_protection | OK
+CONFIG_STRICT_KERNEL_RWX | y |defconfig | self_protection | OK
+CONFIG_STRICT_MODULE_RWX | y |defconfig | self_protection | OK
+CONFIG_REFCOUNT_FULL | y |defconfig | self_protection | FAIL: "is not set"
+CONFIG_IOMMU_SUPPORT | y |defconfig | self_protection | OK
+CONFIG_MICROCODE | y |defconfig | self_protection | OK
+CONFIG_RETPOLINE | y |defconfig | self_protection | OK
+CONFIG_X86_SMAP | y |defconfig | self_protection | OK
+CONFIG_SYN_COOKIES | y |defconfig | self_protection | OK
+CONFIG_X86_UMIP | y |defconfig | self_protection | OK: CONFIG_X86_INTEL_UMIP "y"
+CONFIG_PAGE_TABLE_ISOLATION | y |defconfig | self_protection | OK
+CONFIG_RANDOMIZE_MEMORY | y |defconfig | self_protection | OK
+CONFIG_INTEL_IOMMU | y |defconfig | self_protection | OK
+CONFIG_AMD_IOMMU | y |defconfig | self_protection | OK
+CONFIG_VMAP_STACK | y |defconfig | self_protection | OK
+CONFIG_RANDOMIZE_BASE | y |defconfig | self_protection | OK
+CONFIG_THREAD_INFO_IN_TASK | y |defconfig | self_protection | OK
+CONFIG_BUG_ON_DATA_CORRUPTION | y | kspp | self_protection | FAIL: "is not set"
+CONFIG_DEBUG_WX | y | kspp | self_protection | OK
+CONFIG_SCHED_STACK_END_CHECK | y | kspp | self_protection | OK
+CONFIG_SLAB_FREELIST_HARDENED | y | kspp | self_protection | OK
+CONFIG_SLAB_FREELIST_RANDOM | y | kspp | self_protection | OK
+CONFIG_SHUFFLE_PAGE_ALLOCATOR | y | kspp | self_protection | OK
+CONFIG_FORTIFY_SOURCE | y | kspp | self_protection | OK
+CONFIG_DEBUG_LIST | y | kspp | self_protection | FAIL: "is not set"
+CONFIG_DEBUG_SG | y | kspp | self_protection | FAIL: "is not set"
+CONFIG_DEBUG_CREDENTIALS | y | kspp | self_protection | FAIL: "is not set"
+CONFIG_DEBUG_NOTIFIERS | y | kspp | self_protection | FAIL: "is not set"
+CONFIG_INIT_ON_ALLOC_DEFAULT_ON | y | kspp | self_protection | OK
+CONFIG_GCC_PLUGIN_LATENT_ENTROPY | y | kspp | self_protection | FAIL: not found
+CONFIG_GCC_PLUGIN_RANDSTRUCT | y | kspp | self_protection | FAIL: not found
+CONFIG_HARDENED_USERCOPY | y | kspp | self_protection | OK
+CONFIG_HARDENED_USERCOPY_FALLBACK | is not set | kspp | self_protection | FAIL: "y"
+CONFIG_MODULE_SIG | y | kspp | self_protection | OK
+CONFIG_MODULE_SIG_ALL | y | kspp | self_protection | OK
+CONFIG_MODULE_SIG_SHA512 | y | kspp | self_protection | OK
+CONFIG_MODULE_SIG_FORCE | y | kspp | self_protection | FAIL: "is not set"
+CONFIG_INIT_STACK_ALL | y | kspp | self_protection | FAIL: not found
+CONFIG_INIT_ON_FREE_DEFAULT_ON | y | kspp | self_protection | OK: CONFIG_PAGE_POISONING "y"
+CONFIG_GCC_PLUGIN_STACKLEAK | y | kspp | self_protection | FAIL: not found
+CONFIG_DEFAULT_MMAP_MIN_ADDR | 65536 | kspp | self_protection | OK
+CONFIG_SECURITY_DMESG_RESTRICT | y | clipos | self_protection | FAIL: "is not set"
+CONFIG_DEBUG_VIRTUAL | y | clipos | self_protection | FAIL: "is not set"
+CONFIG_STATIC_USERMODEHELPER | y | clipos | self_protection | FAIL: "is not set"
+CONFIG_SLAB_MERGE_DEFAULT | is not set | clipos | self_protection | FAIL: "y"
+CONFIG_RANDOM_TRUST_BOOTLOADER | is not set | clipos | self_protection | FAIL: "y"
+CONFIG_RANDOM_TRUST_CPU | is not set | clipos | self_protection | FAIL: "y"
+CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_RANDSTRUCT is needed
+CONFIG_STACKLEAK_METRICS | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK is needed
+CONFIG_STACKLEAK_RUNTIME_DISABLE | is not set | clipos | self_protection | FAIL: CONFIG_GCC_PLUGIN_STACKLEAK is needed
+CONFIG_INTEL_IOMMU_SVM | y | clipos | self_protection | OK
+CONFIG_INTEL_IOMMU_DEFAULT_ON | y | clipos | self_protection | FAIL: "is not set"
+CONFIG_SLUB_DEBUG_ON | y | my | self_protection | FAIL: "is not set"
+CONFIG_RESET_ATTACK_MITIGATION | y | my | self_protection | OK
+CONFIG_AMD_IOMMU_V2 | y | my | self_protection | FAIL: "m"
+CONFIG_SECURITY | y |defconfig | security_policy | OK
+CONFIG_SECURITY_YAMA | y | kspp | security_policy | OK
+CONFIG_SECURITY_WRITABLE_HOOKS | is not set | my | security_policy | OK: not found
+CONFIG_SECURITY_LOCKDOWN_LSM | y | clipos | security_policy | OK
+CONFIG_SECURITY_LOCKDOWN_LSM_EARLY | y | clipos | security_policy | OK
+CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY| y | clipos | security_policy | FAIL: "is not set"
+CONFIG_SECURITY_SAFESETID | y | my | security_policy | OK
+CONFIG_SECURITY_LOADPIN | y | my | security_policy | FAIL: "is not set"
+CONFIG_SECURITY_LOADPIN_ENFORCE | y | my | security_policy | FAIL: CONFIG_SECURITY_LOADPIN is needed
+CONFIG_SECCOMP | y |defconfig | cut_attack_surface | OK
+CONFIG_SECCOMP_FILTER | y |defconfig | cut_attack_surface | OK
+CONFIG_STRICT_DEVMEM | y |defconfig | cut_attack_surface | OK
+CONFIG_ACPI_CUSTOM_METHOD | is not set | kspp | cut_attack_surface | OK
+CONFIG_COMPAT_BRK | is not set | kspp | cut_attack_surface | OK
+CONFIG_DEVKMEM | is not set | kspp | cut_attack_surface | OK
+CONFIG_COMPAT_VDSO | is not set | kspp | cut_attack_surface | OK
+CONFIG_BINFMT_MISC | is not set | kspp | cut_attack_surface | FAIL: "m"
+CONFIG_INET_DIAG | is not set | kspp | cut_attack_surface | FAIL: "m"
+CONFIG_KEXEC | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_PROC_KCORE | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_LEGACY_PTYS | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_HIBERNATION | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_IA32_EMULATION | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_X86_X32 | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_MODIFY_LDT_SYSCALL | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_OABI_COMPAT | is not set | kspp | cut_attack_surface | OK: not found
+CONFIG_MODULES | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_DEVMEM | is not set | kspp | cut_attack_surface | FAIL: "y"
+CONFIG_IO_STRICT_DEVMEM | y | kspp | cut_attack_surface | FAIL: "is not set"
+CONFIG_LEGACY_VSYSCALL_NONE | y | kspp | cut_attack_surface | FAIL: "is not set"
+CONFIG_X86_PTDUMP | is not set |grsecurity| cut_attack_surface | OK
+CONFIG_ZSMALLOC_STAT | is not set |grsecurity| cut_attack_surface | OK
+CONFIG_PAGE_OWNER | is not set |grsecurity| cut_attack_surface | OK
+CONFIG_DEBUG_KMEMLEAK | is not set |grsecurity| cut_attack_surface | OK
+CONFIG_BINFMT_AOUT | is not set |grsecurity| cut_attack_surface | OK: not found
+CONFIG_KPROBES | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_UPROBES | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_GENERIC_TRACER | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_PROC_VMCORE | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_PROC_PAGE_MONITOR | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_USELIB | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_CHECKPOINT_RESTORE | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_USERFAULTFD | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_HWPOISON_INJECT | is not set |grsecurity| cut_attack_surface | FAIL: "m"
+CONFIG_MEM_SOFT_DIRTY | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_DEVPORT | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_DEBUG_FS | is not set |grsecurity| cut_attack_surface | FAIL: "y"
+CONFIG_NOTIFIER_ERROR_INJECTION | is not set |grsecurity| cut_attack_surface | FAIL: "m"
+CONFIG_DRM_LEGACY | is not set |maintainer| cut_attack_surface | OK
+CONFIG_FB | is not set |maintainer| cut_attack_surface | FAIL: "y"
+CONFIG_VT | is not set |maintainer| cut_attack_surface | FAIL: "y"
+CONFIG_ACPI_TABLE_UPGRADE | is not set | lockdown | cut_attack_surface | FAIL: "y"
+CONFIG_X86_IOPL_IOPERM | is not set | lockdown | cut_attack_surface | OK: not found
+CONFIG_EFI_TEST | is not set | lockdown | cut_attack_surface | FAIL: "m"
+CONFIG_BPF_SYSCALL | is not set | lockdown | cut_attack_surface | FAIL: "y"
+CONFIG_MMIOTRACE_TEST | is not set | lockdown | cut_attack_surface | OK
+CONFIG_STAGING | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_KSM | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_KALLSYMS | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_X86_VSYSCALL_EMULATION | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_MAGIC_SYSRQ | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_KEXEC_FILE | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_USER_NS | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_X86_MSR | is not set | clipos | cut_attack_surface | FAIL: "m"
+CONFIG_X86_CPUID | is not set | clipos | cut_attack_surface | FAIL: "m"
+CONFIG_LDISC_AUTOLOAD | is not set | clipos | cut_attack_surface | FAIL: "y"
+CONFIG_X86_INTEL_TSX_MODE_OFF | y | clipos | cut_attack_surface | OK
+CONFIG_AIO | is not set |grapheneos| cut_attack_surface | FAIL: "y"
+CONFIG_MMIOTRACE | is not set | my | cut_attack_surface | FAIL: "y"
+CONFIG_LIVEPATCH | is not set | my | cut_attack_surface | FAIL: "y"
+CONFIG_IP_DCCP | is not set | my | cut_attack_surface | FAIL: "m"
+CONFIG_IP_SCTP | is not set | my | cut_attack_surface | FAIL: "m"
+CONFIG_FTRACE | is not set | my | cut_attack_surface | FAIL: "y"
+CONFIG_BPF_JIT | is not set | my | cut_attack_surface | FAIL: "y"
+CONFIG_VIDEO_VIVID | is not set | my | cut_attack_surface | FAIL: "m"
+CONFIG_INPUT_EVBUG | is not set | my | cut_attack_surface | FAIL: "m"
+CONFIG_INTEGRITY | y |defconfig |userspace_hardening | OK
+CONFIG_ARCH_MMAP_RND_BITS | 32 | clipos |userspace_hardening | FAIL: "28"
-[1]: http://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings
+[+] Config check is finished: 'OK' - 57 / 'FAIL' - 79
+```
+
+## kconfig-hardened-check versioning
+
+I usually update the kernel hardening recommendations after each Linux kernel release.
+
+So the version of `kconfig-hardened-check` is associated with the corresponding version of the kernel.
+
+The version format is: __[major_number].[kernel_version].[kernel_patchlevel]__
+
+
+## Questions and answers
+
+__Q:__ How disabling `CONFIG_USER_NS` cuts the attack surface? It's needed for containers!
+
+__A:__ Yes, the `CONFIG_USER_NS` option provides some isolation between the userspace programs,
+but the tool recommends disabling it to cut the attack surface __of the kernel__.
+The rationale:
+
+ - A nice LWN article about the corresponding LKML discussion: https://lwn.net/Articles/673597/
+
+ - A twitter thread about `CONFIG_USER_NS` and security: https://twitter.com/robertswiecki/status/1095447678949953541
+
+ - A good overview of the trade-off between having user namespaces enabled, disabled and available only for root: https://github.com/NixOS/nixpkgs/pull/84522#issuecomment-614640601
+
+<br />
+
+__Q:__ Why `CONFIG_GCC_PLUGINS` is automatically disabled during the kernel compilation?
+
+__A:__ It means that your gcc doesn't support plugins. For example, if you have `gcc-7` on Ubuntu,
+try to install `gcc-7-plugin-dev` package, it should help.
+
+<br />
+
+__Q:__ KSPP and CLIP OS recommend `CONFIG_PANIC_ON_OOPS=y`. Why doesn't this tool do the same?
+
+__A:__ I personally don't support this recommendation because it provides easy denial-of-service
+attacks for the whole system (kernel oops is not a rare situation). I think having `CONFIG_BUG` is enough here --
+if we have a kernel oops in the process context, the offending/attacking process is killed.
+
+<br />
+
+__Q:__ What about performance impact of these kernel hardening options?
+
+__A:__ Ike Devolder [@BlackIkeEagle][7] made some performance tests and described the results in [this article][8].
+
+<br />
+
+__Q:__ Why enabling `CONFIG_STATIC_USERMODEHELPER` breaks various things in my GNU/Linux system?
+Do I really need that feature?
+
+__A:__ Linux kernel usermode helpers can be used for privilege escalation in kernel exploits
+([example 1][9], [example 2][10]). `CONFIG_STATIC_USERMODEHELPER` prevents that method. But it
+requires the corresponding support in the userspace: see the [example implementation][11] by
+Tycho Andersen [@tych0][12].
+
+
+[1]: http://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project/Recommended_Settings
+[2]: https://docs.clip-os.org/clipos/kernel.html#configuration
+[3]: https://grsecurity.net/
+[4]: https://github.com/a13xp0p0v/linux-kernel-defence-map
+[5]: https://lwn.net/Articles/791863/
+[6]: https://github.com/a13xp0p0v/kconfig-hardened-check/issues/38
+[7]: https://github.com/BlackIkeEagle
+[8]: https://blog.herecura.eu/blog/2020-05-30-kconfig-hardening-tests/
+[9]: https://googleprojectzero.blogspot.com/2018/09/a-cache-invalidation-bug-in-linux.html
+[10]: https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html
+[11]: https://github.com/tych0/huldufolk
+[12]: https://github.com/tych0