Revision 3dbae15538972c9e1578cb216964c2840361a538 authored by Gustavo A. R. Silva on 15 February 2020, 01:03:12 UTC, committed by Dmitry Torokhov on 15 February 2020, 01:19:22 UTC
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20200214172132.GA28389@embeddedor
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
1 parent 94bef5d
Makefile.kasan
# SPDX-License-Identifier: GPL-2.0
ifdef CONFIG_KASAN
CFLAGS_KASAN_NOSANITIZE := -fno-builtin
KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
endif
ifdef CONFIG_KASAN_GENERIC
ifdef CONFIG_KASAN_INLINE
call_threshold := 10000
else
call_threshold := 0
endif
CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
# -fasan-shadow-offset fails without -fsanitize
CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET), \
$(call cc-option, -fsanitize=kernel-address \
-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))
ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
else
# Now add all the compiler specific options that are valid standalone
CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
$(call cc-param,asan-globals=1) \
$(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
$(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
$(call cc-param,asan-instrument-allocas=1)
endif
endif # CONFIG_KASAN_GENERIC
ifdef CONFIG_KASAN_SW_TAGS
ifdef CONFIG_KASAN_INLINE
instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
else
instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
endif
CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
-mllvm -hwasan-instrument-stack=0 \
$(instrumentation_flags)
endif # CONFIG_KASAN_SW_TAGS
Computing file changes ...
