fortify: fix warnings in fortify tests with KASAN

[PATCH] fortify: fix warnings in fortify tests with KASAN

Posted by Masahiro Yamada 1 year, 5 months ago

When a software KASAN mode is enabled, the fortify tests emit warnings
on some architectures.

For example, for ARCH=arm, the combination of CONFIG_FORTIFY_SOURCE=y
and CONFIG_KASAN=y produces the following warnings:

    TEST    lib/test_fortify/read_overflow-memchr.log
  warning: unsafe memchr() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memchr.c
    TEST    lib/test_fortify/read_overflow-memchr_inv.log
  warning: unsafe memchr_inv() usage lacked '__read_overflow' symbol in lib/test_fortify/read_overflow-memchr_inv.c
    TEST    lib/test_fortify/read_overflow-memcmp.log
  warning: unsafe memcmp() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memcmp.c
    TEST    lib/test_fortify/read_overflow-memscan.log
  warning: unsafe memscan() usage lacked '__read_overflow' symbol in lib/test_fortify/read_overflow-memscan.c
    TEST    lib/test_fortify/read_overflow2-memcmp.log
  warning: unsafe memcmp() usage lacked '__read_overflow2' warning in lib/test_fortify/read_overflow2-memcmp.c
     [ more and more similar warnings... ]

Commit 9c2d1328f88a ("kbuild: provide reasonable defaults for tool
coverage") removed KASAN flags from non-kernel objects by default.
It was an intended behavior because lib/test_fortify/*.c are unit
tests that are not linked to the kernel.

As it turns out, some architectures require -fsanitize=kernel-(hw)address
to define __SANITIZE_ADDRESS__ for the fortify tests.

Without __SANITIZE_ADDRESS__ defined, arch/arm/include/asm/string.h
defines __NO_FORTIFY, thus excluding <linux/fortify-string.h>.

This issue does not occur on x86 thanks to commit 4ec4190be4cf
("kasan, x86: don't rename memintrinsics in uninstrumented files"),
but there are still some architectures that define __NO_FORTIFY
in such a situation.

Set KASAN_SANITIZE=y explicitly to the fortify tests.

Fixes: 9c2d1328f88a ("kbuild: provide reasonable defaults for tool coverage")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/all/0e8dee26-41cc-41ae-9493-10cd1a8e3268@app.fastmail.com/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

Kees Cook said "I'll try to figure this out", but I have not seen a patch so far,
so I decided to do this myself.
(https://lore.kernel.org/all/202405310908.A5733DF@keescook/)

I will send a pull req with this and some other fixes.
I need to fix this, as v6.10 will be released soon.



 lib/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/Makefile b/lib/Makefile
index 3b1769045651..30337431d10e 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -426,3 +426,7 @@ $(obj)/$(TEST_FORTIFY_LOG): $(addprefix $(obj)/, $(TEST_FORTIFY_LOGS)) FORCE
 ifeq ($(CONFIG_FORTIFY_SOURCE),y)
 $(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)
 endif
+
+# Some architectures define __NO_FORTIFY if __SANITIZE_ADDRESS__ is undefined.
+# Pass CFLAGS_KASAN to avoid warnings.
+$(foreach x, $(patsubst %.log,%.o,$(TEST_FORTIFY_LOGS)), $(eval KASAN_SANITIZE_$(x) := y))
-- 
2.43.0

Re: [PATCH] fortify: fix warnings in fortify tests with KASAN

Posted by Kees Cook 1 year, 5 months ago


On July 14, 2024 10:04:32 AM PDT, Masahiro Yamada <masahiroy@kernel.org> wrote:
>When a software KASAN mode is enabled, the fortify tests emit warnings
>on some architectures.
>
>For example, for ARCH=arm, the combination of CONFIG_FORTIFY_SOURCE=y
>and CONFIG_KASAN=y produces the following warnings:
>
>    TEST    lib/test_fortify/read_overflow-memchr.log
>  warning: unsafe memchr() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memchr.c
>    TEST    lib/test_fortify/read_overflow-memchr_inv.log
>  warning: unsafe memchr_inv() usage lacked '__read_overflow' symbol in lib/test_fortify/read_overflow-memchr_inv.c
>    TEST    lib/test_fortify/read_overflow-memcmp.log
>  warning: unsafe memcmp() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memcmp.c
>    TEST    lib/test_fortify/read_overflow-memscan.log
>  warning: unsafe memscan() usage lacked '__read_overflow' symbol in lib/test_fortify/read_overflow-memscan.c
>    TEST    lib/test_fortify/read_overflow2-memcmp.log
>  warning: unsafe memcmp() usage lacked '__read_overflow2' warning in lib/test_fortify/read_overflow2-memcmp.c
>     [ more and more similar warnings... ]
>
>Commit 9c2d1328f88a ("kbuild: provide reasonable defaults for tool
>coverage") removed KASAN flags from non-kernel objects by default.
>It was an intended behavior because lib/test_fortify/*.c are unit
>tests that are not linked to the kernel.
>
>As it turns out, some architectures require -fsanitize=kernel-(hw)address
>to define __SANITIZE_ADDRESS__ for the fortify tests.
>
>Without __SANITIZE_ADDRESS__ defined, arch/arm/include/asm/string.h
>defines __NO_FORTIFY, thus excluding <linux/fortify-string.h>.
>
>This issue does not occur on x86 thanks to commit 4ec4190be4cf
>("kasan, x86: don't rename memintrinsics in uninstrumented files"),
>but there are still some architectures that define __NO_FORTIFY
>in such a situation.
>
>Set KASAN_SANITIZE=y explicitly to the fortify tests.
>
>Fixes: 9c2d1328f88a ("kbuild: provide reasonable defaults for tool coverage")
>Reported-by: Arnd Bergmann <arnd@arndb.de>
>Closes: https://lore.kernel.org/all/0e8dee26-41cc-41ae-9493-10cd1a8e3268@app.fastmail.com/
>Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>---
>
>Kees Cook said "I'll try to figure this out", but I have not seen a patch so far,
>so I decided to do this myself.
>(https://lore.kernel.org/all/202405310908.A5733DF@keescook/)
>
>I will send a pull req with this and some other fixes.
>I need to fix this, as v6.10 will be released soon.

Awesome! Thanks for figuring this out; I hadn't had time yet. 

Acked-by: Kees Cook<kees@kernel.org>


-- 
Kees Cook

Re: [PATCH] fortify: fix warnings in fortify tests with KASAN

Posted by Masahiro Yamada 1 year, 5 months ago

On Mon, Jul 15, 2024 at 2:09 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> When a software KASAN mode is enabled, the fortify tests emit warnings
> on some architectures.
>
> For example, for ARCH=arm, the combination of CONFIG_FORTIFY_SOURCE=y
> and CONFIG_KASAN=y produces the following warnings:
>
>     TEST    lib/test_fortify/read_overflow-memchr.log
>   warning: unsafe memchr() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memchr.c
>     TEST    lib/test_fortify/read_overflow-memchr_inv.log
>   warning: unsafe memchr_inv() usage lacked '__read_overflow' symbol in lib/test_fortify/read_overflow-memchr_inv.c
>     TEST    lib/test_fortify/read_overflow-memcmp.log
>   warning: unsafe memcmp() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memcmp.c
>     TEST    lib/test_fortify/read_overflow-memscan.log
>   warning: unsafe memscan() usage lacked '__read_overflow' symbol in lib/test_fortify/read_overflow-memscan.c
>     TEST    lib/test_fortify/read_overflow2-memcmp.log
>   warning: unsafe memcmp() usage lacked '__read_overflow2' warning in lib/test_fortify/read_overflow2-memcmp.c
>      [ more and more similar warnings... ]
>
> Commit 9c2d1328f88a ("kbuild: provide reasonable defaults for tool
> coverage") removed KASAN flags from non-kernel objects by default.
> It was an intended behavior because lib/test_fortify/*.c are unit
> tests that are not linked to the kernel.
>
> As it turns out, some architectures require -fsanitize=kernel-(hw)address
> to define __SANITIZE_ADDRESS__ for the fortify tests.
>
> Without __SANITIZE_ADDRESS__ defined, arch/arm/include/asm/string.h
> defines __NO_FORTIFY, thus excluding <linux/fortify-string.h>.
>
> This issue does not occur on x86 thanks to commit 4ec4190be4cf
> ("kasan, x86: don't rename memintrinsics in uninstrumented files"),
> but there are still some architectures that define __NO_FORTIFY
> in such a situation.
>
> Set KASAN_SANITIZE=y explicitly to the fortify tests.
>
> Fixes: 9c2d1328f88a ("kbuild: provide reasonable defaults for tool coverage")
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Closes: https://lore.kernel.org/all/0e8dee26-41cc-41ae-9493-10cd1a8e3268@app.fastmail.com/
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---

Applied to linux-kbuild.



-- 
Best Regards
Masahiro Yamada