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authorLinus Torvalds <torvalds@linux-foundation.org>2019-05-07 12:44:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-07 12:44:49 -0700
commit2d60d96b6f00de90ec2bc60eb4cdcc46e1e1f161 (patch)
tree32f01785f971d37bfe5521d0af978462a0a33dfb /security
parenteac7078a0fff1e72cf2b641721e3f55ec7e5e21e (diff)
parent709a972efb01efaeb97cad1adc87fe400119c8ab (diff)
downloadlwn-2d60d96b6f00de90ec2bc60eb4cdcc46e1e1f161.tar.gz
lwn-2d60d96b6f00de90ec2bc60eb4cdcc46e1e1f161.zip
Merge tag 'meminit-v5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull compiler-based variable initialization updates from Kees Cook: "This is effectively part of my gcc-plugins tree, but as this adds some Clang support, it felt weird to still call it "gcc-plugins". :) This consolidates Kconfig for the existing stack variable initialization (via structleak and stackleak gcc plugins) and adds Alexander Potapenko's support for Clang's new similar functionality. Summary: - Consolidate memory initialization Kconfigs (Kees) - Implement support for Clang's stack variable auto-init (Alexander)" * tag 'meminit-v5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: security: Implement Clang's stack initialization security: Move stackleak config to Kconfig.hardening security: Create "kernel hardening" config area
Diffstat (limited to 'security')
-rw-r--r--security/Kconfig2
-rw-r--r--security/Kconfig.hardening164
2 files changed, 166 insertions, 0 deletions
diff --git a/security/Kconfig b/security/Kconfig
index 353cfef71d4e..aeac3676dd4d 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -287,5 +287,7 @@ config LSM
If unsure, leave this as the default.
+source "security/Kconfig.hardening"
+
endmenu
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
new file mode 100644
index 000000000000..0a1d4ca314f4
--- /dev/null
+++ b/security/Kconfig.hardening
@@ -0,0 +1,164 @@
+menu "Kernel hardening options"
+
+config GCC_PLUGIN_STRUCTLEAK
+ bool
+ help
+ While the kernel is built with warnings enabled for any missed
+ stack variable initializations, this warning is silenced for
+ anything passed by reference to another function, under the
+ occasionally misguided assumption that the function will do
+ the initialization. As this regularly leads to exploitable
+ flaws, this plugin is available to identify and zero-initialize
+ such variables, depending on the chosen level of coverage.
+
+ This plugin was originally ported from grsecurity/PaX. More
+ information at:
+ * https://grsecurity.net/
+ * https://pax.grsecurity.net/
+
+menu "Memory initialization"
+
+config CC_HAS_AUTO_VAR_INIT
+ def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
+
+choice
+ prompt "Initialize kernel stack variables at function entry"
+ default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS
+ default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT
+ default INIT_STACK_NONE
+ help
+ This option enables initialization of stack variables at
+ function entry time. This has the possibility to have the
+ greatest coverage (since all functions can have their
+ variables initialized), but the performance impact depends
+ on the function calling complexity of a given workload's
+ syscalls.
+
+ This chooses the level of coverage over classes of potentially
+ uninitialized variables. The selected class will be
+ initialized before use in a function.
+
+ config INIT_STACK_NONE
+ bool "no automatic initialization (weakest)"
+ help
+ Disable automatic stack variable initialization.
+ This leaves the kernel vulnerable to the standard
+ classes of uninitialized stack variable exploits
+ and information exposures.
+
+ config GCC_PLUGIN_STRUCTLEAK_USER
+ bool "zero-init structs marked for userspace (weak)"
+ depends on GCC_PLUGINS
+ select GCC_PLUGIN_STRUCTLEAK
+ help
+ Zero-initialize any structures on the stack containing
+ a __user attribute. This can prevent some classes of
+ uninitialized stack variable exploits and information
+ exposures, like CVE-2013-2141:
+ https://git.kernel.org/linus/b9e146d8eb3b9eca
+
+ config GCC_PLUGIN_STRUCTLEAK_BYREF
+ bool "zero-init structs passed by reference (strong)"
+ depends on GCC_PLUGINS
+ select GCC_PLUGIN_STRUCTLEAK
+ help
+ Zero-initialize any structures on the stack that may
+ be passed by reference and had not already been
+ explicitly initialized. This can prevent most classes
+ of uninitialized stack variable exploits and information
+ exposures, like CVE-2017-1000410:
+ https://git.kernel.org/linus/06e7e776ca4d3654
+
+ config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
+ bool "zero-init anything passed by reference (very strong)"
+ depends on GCC_PLUGINS
+ select GCC_PLUGIN_STRUCTLEAK
+ help
+ Zero-initialize any stack variables that may be passed
+ by reference and had not already been explicitly
+ initialized. This is intended to eliminate all classes
+ of uninitialized stack variable exploits and information
+ exposures.
+
+ config INIT_STACK_ALL
+ bool "0xAA-init everything on the stack (strongest)"
+ depends on CC_HAS_AUTO_VAR_INIT
+ help
+ Initializes everything on the stack with a 0xAA
+ pattern. This is intended to eliminate all classes
+ of uninitialized stack variable exploits and information
+ exposures, even variables that were warned to have been
+ left uninitialized.
+
+endchoice
+
+config GCC_PLUGIN_STRUCTLEAK_VERBOSE
+ bool "Report forcefully initialized variables"
+ depends on GCC_PLUGIN_STRUCTLEAK
+ depends on !COMPILE_TEST # too noisy
+ help
+ This option will cause a warning to be printed each time the
+ structleak plugin finds a variable it thinks needs to be
+ initialized. Since not all existing initializers are detected
+ by the plugin, this can produce false positive warnings.
+
+config GCC_PLUGIN_STACKLEAK
+ bool "Poison kernel stack before returning from syscalls"
+ depends on GCC_PLUGINS
+ depends on HAVE_ARCH_STACKLEAK
+ help
+ This option makes the kernel erase the kernel stack before
+ returning from system calls. This has the effect of leaving
+ the stack initialized to the poison value, which both reduces
+ the lifetime of any sensitive stack contents and reduces
+ potential for uninitialized stack variable exploits or information
+ exposures (it does not cover functions reaching the same stack
+ depth as prior functions during the same syscall). This blocks
+ most uninitialized stack variable attacks, with the performance
+ impact being driven by the depth of the stack usage, rather than
+ the function calling complexity.
+
+ The performance impact on a single CPU system kernel compilation
+ sees a 1% slowdown, other systems and workloads may vary and you
+ are advised to test this feature on your expected workload before
+ deploying it.
+
+ This plugin was ported from grsecurity/PaX. More information at:
+ * https://grsecurity.net/
+ * https://pax.grsecurity.net/
+
+config STACKLEAK_TRACK_MIN_SIZE
+ int "Minimum stack frame size of functions tracked by STACKLEAK"
+ default 100
+ range 0 4096
+ depends on GCC_PLUGIN_STACKLEAK
+ help
+ The STACKLEAK gcc plugin instruments the kernel code for tracking
+ the lowest border of the kernel stack (and for some other purposes).
+ It inserts the stackleak_track_stack() call for the functions with
+ a stack frame size greater than or equal to this parameter.
+ If unsure, leave the default value 100.
+
+config STACKLEAK_METRICS
+ bool "Show STACKLEAK metrics in the /proc file system"
+ depends on GCC_PLUGIN_STACKLEAK
+ depends on PROC_FS
+ help
+ If this is set, STACKLEAK metrics for every task are available in
+ the /proc file system. In particular, /proc/<pid>/stack_depth
+ shows the maximum kernel stack consumption for the current and
+ previous syscalls. Although this information is not precise, it
+ can be useful for estimating the STACKLEAK performance impact for
+ your workloads.
+
+config STACKLEAK_RUNTIME_DISABLE
+ bool "Allow runtime disabling of kernel stack erasing"
+ depends on GCC_PLUGIN_STACKLEAK
+ help
+ This option provides 'stack_erasing' sysctl, which can be used in
+ runtime to control kernel stack erasing for kernels built with
+ CONFIG_GCC_PLUGIN_STACKLEAK.
+
+endmenu
+
+endmenu