mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-25 03:55:09 +08:00
277a10850f
In order to do kernel builds with the bounds checker individually
available, introduce CONFIG_UBSAN_BOUNDS, with the remaining options under
CONFIG_UBSAN_MISC.
For example, using this, we can start to expand the coverage syzkaller is
providing. Right now, all of UBSan is disabled for syzbot builds because
taken as a whole, it is too noisy. This will let us focus on one feature
at a time.
For the bounds checker specifically, this provides a mechanism to
eliminate an entire class of array overflows with close to zero
performance overhead (I cannot measure a difference). In my (mostly)
defconfig, enabling bounds checking adds ~4200 checks to the kernel.
Performance changes are in the noise, likely due to the branch predictors
optimizing for the non-fail path.
Some notes on the bounds checker:
- it does not instrument {mem,str}*()-family functions, it only
instruments direct indexed accesses (e.g. "foo[i]"). Dealing with
the {mem,str}*()-family functions is a work-in-progress around
CONFIG_FORTIFY_SOURCE[1].
- it ignores flexible array members, including the very old single
byte (e.g. "int foo[1];") declarations. (Note that GCC's
implementation appears to ignore _all_ trailing arrays, but Clang only
ignores empty, 0, and 1 byte arrays[2].)
[1] https://github.com/KSPP/linux/issues/6
[2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92589
Suggested-by: Elena Petrova <lenaptr@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Link: http://lkml.kernel.org/r/20200227193516.32566-3-keescook@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
83 lines
2.9 KiB
Plaintext
83 lines
2.9 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
|
|
config ARCH_HAS_UBSAN_SANITIZE_ALL
|
|
bool
|
|
|
|
menuconfig UBSAN
|
|
bool "Undefined behaviour sanity checker"
|
|
help
|
|
This option enables the Undefined Behaviour sanity checker.
|
|
Compile-time instrumentation is used to detect various undefined
|
|
behaviours at runtime. For more details, see:
|
|
Documentation/dev-tools/ubsan.rst
|
|
|
|
if UBSAN
|
|
|
|
config UBSAN_TRAP
|
|
bool "On Sanitizer warnings, abort the running kernel code"
|
|
depends on $(cc-option, -fsanitize-undefined-trap-on-error)
|
|
help
|
|
Building kernels with Sanitizer features enabled tends to grow
|
|
the kernel size by around 5%, due to adding all the debugging
|
|
text on failure paths. To avoid this, Sanitizer instrumentation
|
|
can just issue a trap. This reduces the kernel size overhead but
|
|
turns all warnings (including potentially harmless conditions)
|
|
into full exceptions that abort the running kernel code
|
|
(regardless of context, locks held, etc), which may destabilize
|
|
the system. For some system builders this is an acceptable
|
|
trade-off.
|
|
|
|
config UBSAN_BOUNDS
|
|
bool "Perform array index bounds checking"
|
|
default UBSAN
|
|
help
|
|
This option enables detection of directly indexed out of bounds
|
|
array accesses, where the array size is known at compile time.
|
|
Note that this does not protect array overflows via bad calls
|
|
to the {str,mem}*cpy() family of functions (that is addressed
|
|
by CONFIG_FORTIFY_SOURCE).
|
|
|
|
config UBSAN_MISC
|
|
bool "Enable all other Undefined Behavior sanity checks"
|
|
default UBSAN
|
|
help
|
|
This option enables all sanity checks that don't have their
|
|
own Kconfig options. Disable this if you only want to have
|
|
individually selected checks.
|
|
|
|
config UBSAN_SANITIZE_ALL
|
|
bool "Enable instrumentation for the entire kernel"
|
|
depends on ARCH_HAS_UBSAN_SANITIZE_ALL
|
|
|
|
# We build with -Wno-maybe-uninitilzed, but we still want to
|
|
# use -Wmaybe-uninitilized in allmodconfig builds.
|
|
# So dependsy bellow used to disable this option in allmodconfig
|
|
depends on !COMPILE_TEST
|
|
default y
|
|
help
|
|
This option activates instrumentation for the entire kernel.
|
|
If you don't enable this option, you have to explicitly specify
|
|
UBSAN_SANITIZE := y for the files/directories you want to check for UB.
|
|
Enabling this option will get kernel image size increased
|
|
significantly.
|
|
|
|
config UBSAN_NO_ALIGNMENT
|
|
bool "Disable checking of pointers alignment"
|
|
default y if HAVE_EFFICIENT_UNALIGNED_ACCESS
|
|
help
|
|
This option disables the check of unaligned memory accesses.
|
|
This option should be used when building allmodconfig.
|
|
Disabling this option on architectures that support unaligned
|
|
accesses may produce a lot of false positives.
|
|
|
|
config UBSAN_ALIGNMENT
|
|
def_bool !UBSAN_NO_ALIGNMENT
|
|
|
|
config TEST_UBSAN
|
|
tristate "Module for testing for undefined behavior detection"
|
|
depends on m
|
|
help
|
|
This is a test module for UBSAN.
|
|
It triggers various undefined behavior, and detect it.
|
|
|
|
endif # if UBSAN
|