6c7a7ca606
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
Bug: 136249967
commit b93f1a29fa5d ("FROMLIST: ubsan: Split bounds checker from other options")
https://android.googlesource.com/kernel/common android-mainline
Link: https://lore.kernel.org/kernel-hardening/20191121181519.28637-3-keescook@chromium.org/
Suggested-by: Elena Petrova <lenaptr@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Elena Petrova <lenaptr@google.com>
Change-Id: I1ea057bf3a63bd167206a00022e5e485b8f61f81
31 lines
1.1 KiB
Makefile
31 lines
1.1 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
|
|
ifdef CONFIG_UBSAN
|
|
|
|
ifdef CONFIG_UBSAN_ALIGNMENT
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
|
|
endif
|
|
|
|
ifdef CONFIG_UBSAN_BOUNDS
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
|
|
endif
|
|
|
|
ifdef CONFIG_UBSAN_MISC
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=shift)
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=integer-divide-by-zero)
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=unreachable)
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=vla-bound)
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=signed-integer-overflow)
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=object-size)
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=bool)
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize=enum)
|
|
endif
|
|
|
|
ifdef CONFIG_UBSAN_TRAP
|
|
CFLAGS_UBSAN += $(call cc-option, -fsanitize-undefined-trap-on-error)
|
|
endif
|
|
|
|
# -fsanitize=* options makes GCC less smart than usual and
|
|
# increase number of 'maybe-uninitialized false-positives
|
|
CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)
|
|
endif
|