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linux/security/Kconfig
Linus Torvalds 599bbba5a3 proc: make PROC_MEM_FORCE_PTRACE the Kconfig default 
This kconfig option was introduced 18 months ago, with the historical
default of always allowing forcing memory permission overrides in order
to not change any existing behavior.

But it was documented as "for now", and this is a gentle nudge to people
that you probably _should_ be using PROC_MEM_FORCE_PTRACE.  I've had
that in my local kernel config since the option was introduced.

Anybody who just does "make oldconfig" will pick up their old
configuration with no change, so this is still meant to not change any
existing system behavior, but at least gently prod people into trying
it.

I'd love to get rid of FOLL_FORCE entirely (see commit 8ee74a91ac
"proc: try to remove use of FOLL_FORCE entirely" from roughly a decade
ago), but sadly that is likely not a realistic option (see commit
f511c0b17b "Yes, people use FOLL_FORCE ;)" three weeks later).

But at least let's make it more obvious that you have the choice to
limit it and force people to at least be a bit more conscious about
their use of FOLL_FORCE, since judging from a recent discussion people
weren't even aware of this one.

Reminded-by: Vova Tokarev <vladimirelitokarev@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2026-04-13 09:12:37 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
#
# Security configuration
#
menu "Security options"
source "security/keys/Kconfig"
config SECURITY_DMESG_RESTRICT
bool "Restrict unprivileged access to the kernel syslog"
default n
help
This enforces restrictions on unprivileged users reading the kernel
syslog via dmesg(8).
If this option is not selected, no restrictions will be enforced
unless the dmesg_restrict sysctl is explicitly set to (1).
If you are unsure how to answer this question, answer N.
choice
prompt "Allow /proc/pid/mem access override"
default PROC_MEM_FORCE_PTRACE
help
Traditionally /proc/pid/mem allows users to override memory
permissions for users like ptrace, assuming they have ptrace
capability.
This allows people to limit that - either never override, or
require actual active ptrace attachment (default).
config PROC_MEM_ALWAYS_FORCE
bool "Traditional /proc/pid/mem behavior"
help
This allows /proc/pid/mem accesses to override memory mapping
permissions if you have ptrace access rights.
config PROC_MEM_FORCE_PTRACE
bool "Require active ptrace() use for access override"
help
This allows /proc/pid/mem accesses to override memory mapping
permissions for active ptracers like gdb.
config PROC_MEM_NO_FORCE
bool "Never"
help
Never override memory mapping permissions
endchoice
config MSEAL_SYSTEM_MAPPINGS
bool "mseal system mappings"
depends on 64BIT
depends on ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
depends on !CHECKPOINT_RESTORE
help
Apply mseal on system mappings.
The system mappings includes vdso, vvar, vvar_vclock,
vectors (arm compat-mode), sigpage (arm compat-mode), uprobes.
A 64-bit kernel is required for the memory sealing feature.
No specific hardware features from the CPU are needed.
WARNING: This feature breaks programs which rely on relocating
or unmapping system mappings. Known broken software at the time
of writing includes CHECKPOINT_RESTORE, UML, gVisor, rr. Therefore
this config can't be enabled universally.
For complete descriptions of memory sealing, please see
Documentation/userspace-api/mseal.rst
config SECURITY
bool "Enable different security models"
depends on SYSFS
depends on MULTIUSER
help
This allows you to choose different security modules to be
configured into your kernel.
If this option is not selected, the default Linux security
model will be used.
If you are unsure how to answer this question, answer N.
config HAS_SECURITY_AUDIT
def_bool y
depends on AUDIT
depends on SECURITY
config SECURITYFS
bool "Enable the securityfs filesystem"
help
This will build the securityfs filesystem. It is currently used by
various security modules (AppArmor, IMA, SafeSetID, TOMOYO, TPM).
If you are unsure how to answer this question, answer N.
config SECURITY_NETWORK
bool "Socket and Networking Security Hooks"
depends on SECURITY
help
This enables the socket and networking security hooks.
If enabled, a security module can use these hooks to
implement socket and networking access controls.
If you are unsure how to answer this question, answer N.
config SECURITY_INFINIBAND
bool "Infiniband Security Hooks"
depends on SECURITY && INFINIBAND
help
This enables the Infiniband security hooks.
If enabled, a security module can use these hooks to
implement Infiniband access controls.
If you are unsure how to answer this question, answer N.
config SECURITY_NETWORK_XFRM
bool "XFRM (IPSec) Networking Security Hooks"
depends on XFRM && SECURITY_NETWORK
help
This enables the XFRM (IPSec) networking security hooks.
If enabled, a security module can use these hooks to
implement per-packet access controls based on labels
derived from IPSec policy. Non-IPSec communications are
designated as unlabelled, and only sockets authorized
to communicate unlabelled data can send without using
IPSec.
If you are unsure how to answer this question, answer N.
config SECURITY_PATH
bool "Security hooks for pathname based access control"
depends on SECURITY
help
This enables the security hooks for pathname based access control.
If enabled, a security module can use these hooks to
implement pathname based access controls.
If you are unsure how to answer this question, answer N.
config INTEL_TXT
bool "Enable Intel(R) Trusted Execution Technology (Intel(R) TXT)"
depends on HAVE_INTEL_TXT
help
This option enables support for booting the kernel with the
Trusted Boot (tboot) module. This will utilize
Intel(R) Trusted Execution Technology to perform a measured launch
of the kernel. If the system does not support Intel(R) TXT, this
will have no effect.
Intel TXT will provide higher assurance of system configuration and
initial state as well as data reset protection. This is used to
create a robust initial kernel measurement and verification, which
helps to ensure that kernel security mechanisms are functioning
correctly. This level of protection requires a root of trust outside
of the kernel itself.
Intel TXT also helps solve real end user concerns about having
confidence that their hardware is running the VMM or kernel that
it was configured with, especially since they may be responsible for
providing such assurances to VMs and services running on it.
See <https://www.intel.com/technology/security/> for more information
about Intel(R) TXT.
See <http://tboot.sourceforge.net> for more information about tboot.
See Documentation/arch/x86/intel_txt.rst for a description of how to enable
Intel TXT support in a kernel boot.
If you are unsure as to whether this is required, answer N.
config LSM_MMAP_MIN_ADDR
int "Low address space for LSM to protect from user allocation"
depends on SECURITY && SECURITY_SELINUX
default 32768 if ARM || (ARM64 && COMPAT)
default 65536
help
This is the portion of low virtual memory which should be protected
from userspace allocation. Keeping a user from writing to low pages
can help reduce the impact of kernel NULL pointer bugs.
For most ia64, ppc64 and x86 users with lots of address space
a value of 65536 is reasonable and should cause no problems.
On arm and other archs it should not be higher than 32768.
Programs which use vm86 functionality or have some need to map
this low address space will need the permission specific to the
systems running LSM.
config STATIC_USERMODEHELPER
bool "Force all usermode helper calls through a single binary"
help
By default, the kernel can call many different userspace
binary programs through the "usermode helper" kernel
interface. Some of these binaries are statically defined
either in the kernel code itself, or as a kernel configuration
option. However, some of these are dynamically created at
runtime, or can be modified after the kernel has started up.
To provide an additional layer of security, route all of these
calls through a single executable that can not have its name
changed.
Note, it is up to this single binary to then call the relevant
"real" usermode helper binary, based on the first argument
passed to it. If desired, this program can filter and pick
and choose what real programs are called.
If you wish for all usermode helper programs are to be
disabled, choose this option and then set
STATIC_USERMODEHELPER_PATH to an empty string.
config STATIC_USERMODEHELPER_PATH
string "Path to the static usermode helper binary"
depends on STATIC_USERMODEHELPER
default "/sbin/usermode-helper"
help
The binary called by the kernel when any usermode helper
program is wish to be run. The "real" application's name will
be in the first argument passed to this program on the command
line.
If you wish for all usermode helper programs to be disabled,
specify an empty string here (i.e. "").
source "security/selinux/Kconfig"
source "security/smack/Kconfig"
source "security/tomoyo/Kconfig"
source "security/apparmor/Kconfig"
source "security/loadpin/Kconfig"
source "security/yama/Kconfig"
source "security/safesetid/Kconfig"
source "security/lockdown/Kconfig"
source "security/landlock/Kconfig"
source "security/ipe/Kconfig"
source "security/integrity/Kconfig"
choice
prompt "First legacy 'major LSM' to be initialized"
default DEFAULT_SECURITY_SELINUX if SECURITY_SELINUX
default DEFAULT_SECURITY_SMACK if SECURITY_SMACK
default DEFAULT_SECURITY_TOMOYO if SECURITY_TOMOYO
default DEFAULT_SECURITY_APPARMOR if SECURITY_APPARMOR
default DEFAULT_SECURITY_DAC
help
This choice is there only for converting CONFIG_DEFAULT_SECURITY
in old kernel configs to CONFIG_LSM in new kernel configs. Don't
change this choice unless you are creating a fresh kernel config,
for this choice will be ignored after CONFIG_LSM has been set.
Selects the legacy "major security module" that will be
initialized first. Overridden by non-default CONFIG_LSM.
config DEFAULT_SECURITY_SELINUX
bool "SELinux" if SECURITY_SELINUX=y
config DEFAULT_SECURITY_SMACK
bool "Simplified Mandatory Access Control" if SECURITY_SMACK=y
config DEFAULT_SECURITY_TOMOYO
bool "TOMOYO" if SECURITY_TOMOYO=y
config DEFAULT_SECURITY_APPARMOR
bool "AppArmor" if SECURITY_APPARMOR=y
config DEFAULT_SECURITY_DAC
bool "Unix Discretionary Access Controls"
endchoice
config LSM
string "Ordered list of enabled LSMs"
depends on SECURITY
default "landlock,lockdown,yama,loadpin,safesetid,smack,selinux,tomoyo,apparmor,ipe,bpf" if DEFAULT_SECURITY_SMACK
default "landlock,lockdown,yama,loadpin,safesetid,apparmor,selinux,smack,tomoyo,ipe,bpf" if DEFAULT_SECURITY_APPARMOR
default "landlock,lockdown,yama,loadpin,safesetid,tomoyo,ipe,bpf" if DEFAULT_SECURITY_TOMOYO
default "landlock,lockdown,yama,loadpin,safesetid,ipe,bpf" if DEFAULT_SECURITY_DAC
default "landlock,lockdown,yama,loadpin,safesetid,selinux,smack,tomoyo,apparmor,ipe,bpf"
help
A comma-separated list of LSMs, in initialization order.
Any LSMs left off this list, except for those with order
LSM_ORDER_FIRST and LSM_ORDER_LAST, which are always enabled
if selected in the kernel configuration, will be ignored.
This can be controlled at boot with the "lsm=" parameter.
If unsure, leave this as the default.
config SECURITY_COMMONCAP_KUNIT_TEST
bool "Build KUnit tests for commoncap" if !KUNIT_ALL_TESTS
depends on KUNIT=y && USER_NS
default KUNIT_ALL_TESTS
help
This builds the commoncap KUnit tests.
KUnit tests run during boot and output the results to the debug log
in TAP format (https://testanything.org/). Only useful for kernel devs
running KUnit test harness and are not for inclusion into a
production build.
For more information on KUnit and unit tests in general please refer
to the KUnit documentation in Documentation/dev-tools/kunit/.
If unsure, say N.
source "security/Kconfig.hardening"
endmenu
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