Introduce CONFIG_SLAB_BUCKETS which provides the infrastructure to
support separated kmalloc buckets (in the following kmem_buckets_create()
patches and future codetag-based separation). Since this will provide
a mitigation for a very common case of exploits, it is recommended to
enable this feature for general purpose distros. By default, the new
Kconfig will be enabled if CONFIG_SLAB_FREELIST_HARDENED is enabled (and
it is added to the hardening.config Kconfig fragment).
To be able to choose which buckets to allocate from, make the buckets
available to the internal kmalloc interfaces by adding them as the
second argument, rather than depending on the buckets being chosen from
the fixed set of global buckets. Where the bucket is not available,
pass NULL, which means "use the default system kmalloc bucket set"
(the prior existing behavior), as implemented in kmalloc_slab().
To avoid adding the extra argument when !CONFIG_SLAB_BUCKETS, only the
top-level macros and static inlines use the buckets argument (where
they are stripped out and compiled out respectively). The actual extern
functions can then be built without the argument, and the internals
fall back to the global kmalloc buckets unconditionally.
Co-developed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Kees Cook <kees@kernel.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
- selftests: Add str*cmp tests (Ivan Orlov)
- __counted_by: provide UAPI for _le/_be variants (Erick Archer)
- Various strncpy deprecation refactors (Justin Stitt)
- stackleak: Use a copy of soon-to-be-const sysctl table (Thomas Weißschuh)
- UBSAN: Work around i386 -regparm=3 bug with Clang prior to version 19
- Provide helper to deal with non-NUL-terminated string copying
- SCSI: Fix older string copying bugs (with new helper)
- selftests: Consolidate string helper behavioral tests
- selftests: add memcpy() fortify tests
- string: Add additional __realloc_size() annotations for "dup" helpers
- LKDTM: Fix KCFI+rodata+objtool confusion
- hardening.config: Enable KCFI
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Merge tag 'hardening-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull hardening updates from Kees Cook:
"The bulk of the changes here are related to refactoring and expanding
the KUnit tests for string helper and fortify behavior.
Some trivial strncpy replacements in fs/ were carried in my tree. Also
some fixes to SCSI string handling were carried in my tree since the
helper for those was introduce here. Beyond that, just little fixes
all around: objtool getting confused about LKDTM+KCFI, preparing for
future refactors (constification of sysctl tables, additional
__counted_by annotations), a Clang UBSAN+i386 crash fix, and adding
more options in the hardening.config Kconfig fragment.
Summary:
- selftests: Add str*cmp tests (Ivan Orlov)
- __counted_by: provide UAPI for _le/_be variants (Erick Archer)
- Various strncpy deprecation refactors (Justin Stitt)
- stackleak: Use a copy of soon-to-be-const sysctl table (Thomas
Weißschuh)
- UBSAN: Work around i386 -regparm=3 bug with Clang prior to
version 19
- Provide helper to deal with non-NUL-terminated string copying
- SCSI: Fix older string copying bugs (with new helper)
- selftests: Consolidate string helper behavioral tests
- selftests: add memcpy() fortify tests
- string: Add additional __realloc_size() annotations for "dup"
helpers
- LKDTM: Fix KCFI+rodata+objtool confusion
- hardening.config: Enable KCFI"
* tag 'hardening-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (29 commits)
uapi: stddef.h: Provide UAPI macros for __counted_by_{le, be}
stackleak: Use a copy of the ctl_table argument
string: Add additional __realloc_size() annotations for "dup" helpers
kunit/fortify: Fix replaced failure path to unbreak __alloc_size
hardening: Enable KCFI and some other options
lkdtm: Disable CFI checking for perms functions
kunit/fortify: Add memcpy() tests
kunit/fortify: Do not spam logs with fortify WARNs
kunit/fortify: Rename tests to use recommended conventions
init: replace deprecated strncpy with strscpy_pad
kunit/fortify: Fix mismatched kvalloc()/vfree() usage
scsi: qla2xxx: Avoid possible run-time warning with long model_num
scsi: mpi3mr: Avoid possible run-time warning with long manufacturer strings
scsi: mptfusion: Avoid possible run-time warning with long manufacturer strings
fs: ecryptfs: replace deprecated strncpy with strscpy
hfsplus: refactor copy_name to not use strncpy
reiserfs: replace deprecated strncpy with scnprintf
virt: acrn: replace deprecated strncpy with strscpy
ubsan: Avoid i386 UBSAN handler crashes with Clang
ubsan: Remove 1-element array usage in debug reporting
...
Add some stuff that got missed along the way:
- CONFIG_UNWIND_PATCH_PAC_INTO_SCS=y so SCS vs PAC is hardware
selectable.
- CONFIG_X86_KERNEL_IBT=y while a default, just be sure.
- CONFIG_CFI_CLANG=y globally.
- CONFIG_PAGE_TABLE_CHECK=y for userspace mapping sanity.
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240501193709.make.982-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
kernel/configs/hardening.config turns on UBSAN for the bounds sanitizer,
as that in combination with trapping can stop the exploitation of buffer
overflows within the kernel. At the same time, hardening.config turns
off every other UBSAN sanitizer because trapping means all UBSAN reports
will be fatal and the problems brought up by other sanitizers generally
do not have security implications.
The signed integer overflow sanitizer was recently added back to the
kernel and it is default on with just CONFIG_UBSAN=y, meaning that it
gets enabled when merging hardening.config into another configuration.
While this sanitizer does have security implications like the array
bounds sanitizer, work to clean up enough instances to allow this to run
in production environments is still ramping up, which means regular
users and testers may be broken by these instances with
CONFIG_UBSAN_TRAP=y. Disable CONFIG_UBSAN_SIGNED_WRAP in
hardening.config to avoid this situation.
Fixes: 557f8c582a ("ubsan: Reintroduce signed overflow sanitizer")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240411-fix-ubsan-in-hardening-config-v1-2-e0177c80ffaa@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
The initial change that added kernel/configs/hardening.config attempted
to disable all UBSAN sanitizers except for the array bounds one while
turning on UBSAN_TRAP. Unfortunately, it only got the syntax for
CONFIG_UBSAN_SHIFT correct, so configurations that are on by default
with CONFIG_UBSAN=y such as CONFIG_UBSAN_{BOOL,ENUM} do not get disabled
properly.
CONFIG_ARCH_HAS_UBSAN=y
CONFIG_UBSAN=y
CONFIG_UBSAN_TRAP=y
CONFIG_CC_HAS_UBSAN_BOUNDS_STRICT=y
CONFIG_UBSAN_BOUNDS=y
CONFIG_UBSAN_BOUNDS_STRICT=y
# CONFIG_UBSAN_SHIFT is not set
# CONFIG_UBSAN_DIV_ZERO is not set
# CONFIG_UBSAN_UNREACHABLE is not set
CONFIG_UBSAN_SIGNED_WRAP=y
CONFIG_UBSAN_BOOL=y
CONFIG_UBSAN_ENUM=y
# CONFIG_TEST_UBSAN is not set
Add the missing 'is not set' to each configuration that needs it so that
they get disabled as intended.
CONFIG_ARCH_HAS_UBSAN=y
CONFIG_UBSAN=y
CONFIG_UBSAN_TRAP=y
CONFIG_CC_HAS_UBSAN_BOUNDS_STRICT=y
CONFIG_UBSAN_BOUNDS=y
CONFIG_UBSAN_BOUNDS_STRICT=y
# CONFIG_UBSAN_SHIFT is not set
# CONFIG_UBSAN_DIV_ZERO is not set
# CONFIG_UBSAN_UNREACHABLE is not set
CONFIG_UBSAN_SIGNED_WRAP=y
# CONFIG_UBSAN_BOOL is not set
# CONFIG_UBSAN_ENUM is not set
# CONFIG_TEST_UBSAN is not set
Fixes: 215199e3d9 ("hardening: Provide Kconfig fragments for basic options")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240411-fix-ubsan-in-hardening-config-v1-1-e0177c80ffaa@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
KFENCE is not a security mitigation mechanism (due to sampling), but has
the performance characteristics of unintrusive hardening techniques.
When used at scale, however, it improves overall security by allowing
kernel developers to detect heap memory-safety bugs cheaply.
Link: https://lkml.kernel.org/r/79B9A832-B3DE-4229-9D87-748B2CFB7D12@kernel.org
Cc: Matthieu Baerts <matttbe@kernel.org>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20240212130116.997627-1-elver@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Commit 94f8f319cb ("drm: Remove Kconfig option for legacy support
(CONFIG_DRM_LEGACY)") removes the config DRM_LEGACY, but one reference to
that config is left in the hardening.config fragment.
As there is no drm legacy driver left, we do not need to recommend this
attack surface reduction anymore.
Drop this reference in hardening.config fragment.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20240208091045.9219-3-lukas.bulwahn@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Commit 7a628f818499 ("ubsan: Remove CONFIG_UBSAN_SANITIZE_ALL") removes the
config UBSAN_SANITIZE_ALL, but one reference to that config is left in the
hardening.config fragment.
Drop this reference in hardening.config fragment.
Note that CONFIG_UBSAN is still enabled in the hardening.config fragment,
so the functionality when using this fragment remains the same.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20240208091045.9219-2-lukas.bulwahn@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Inspired by Salvatore Mesoraca's earlier[1] efforts to provide some
in-tree guidance for kernel hardening Kconfig options, add a new fragment
named "hardening-basic.config" (along with some arch-specific fragments)
that enable a basic set of kernel hardening options that have the least
(or no) performance impact and remove a reasonable set of legacy APIs.
Using this fragment is as simple as running "make hardening.config".
More extreme fragments can be added[2] in the future to cover all the
recognized hardening options, and more per-architecture files can be
added too.
For now, document the fragments directly via comments. Perhaps .rst
documentation can be generated from them in the future (rather than the
other way around).
[1] https://lore.kernel.org/kernel-hardening/1536516257-30871-1-git-send-email-s.mesoraca16@gmail.com/
[2] https://github.com/KSPP/linux/issues/14
Cc: Salvatore Mesoraca <s.mesoraca16@gmail.com>
Cc: x86@kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
