On Wed, Nov 18, 2020 at 12:07:30PM +0100, laniel_francis@xxxxxxxxxxxxxxxxxxx wrote:
> From: Francis Laniel <laniel_francis@xxxxxxxxxxxxxxxxxxx>
>
> This new test ensures that fortified strscpy has the same behavior than vanilla
> strscpy (e.g. returning -E2BIG when src content is truncated).
> Finally, it generates a crash at runtime because there is a write overflow in
> destination string.
>
> Signed-off-by: Francis Laniel <laniel_francis@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> drivers/misc/lkdtm/Makefile | 1 +
> drivers/misc/lkdtm/core.c | 1 +
> drivers/misc/lkdtm/fortify.c | 82 +++++++++++++++++++++++++
> drivers/misc/lkdtm/lkdtm.h | 3 +
> tools/testing/selftests/lkdtm/tests.txt | 1 +
> 5 files changed, 88 insertions(+)
> create mode 100644 drivers/misc/lkdtm/fortify.c
>
> diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
> index c70b3822013f..d898f7b22045 100644
> --- a/drivers/misc/lkdtm/Makefile
> +++ b/drivers/misc/lkdtm/Makefile
> @@ -10,6 +10,7 @@ lkdtm-$(CONFIG_LKDTM) += rodata_objcopy.o
> lkdtm-$(CONFIG_LKDTM) += usercopy.o
> lkdtm-$(CONFIG_LKDTM) += stackleak.o
> lkdtm-$(CONFIG_LKDTM) += cfi.o
> +lkdtm-$(CONFIG_LKDTM) += fortify.o
>
> KASAN_SANITIZE_stackleak.o := n
> KCOV_INSTRUMENT_rodata.o := n
> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> index b8c51a633fcc..3c0a67f072c0 100644
> --- a/drivers/misc/lkdtm/core.c
> +++ b/drivers/misc/lkdtm/core.c
> @@ -175,6 +175,7 @@ static const struct crashtype crashtypes[] = {
> CRASHTYPE(USERCOPY_KERNEL),
> CRASHTYPE(STACKLEAK_ERASING),
> CRASHTYPE(CFI_FORWARD_PROTO),
> + CRASHTYPE(FORTIFIED_STRSCPY),
> #ifdef CONFIG_X86_32
> CRASHTYPE(DOUBLE_FAULT),
> #endif
> diff --git a/drivers/misc/lkdtm/fortify.c b/drivers/misc/lkdtm/fortify.c
> new file mode 100644
> index 000000000000..790d46591bf5
> --- /dev/null
> +++ b/drivers/misc/lkdtm/fortify.c
> @@ -0,0 +1,82 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2020 Francis Laniel <laniel_francis@xxxxxxxxxxxxxxxxxxx>
> + *
> + * Add tests related to fortified functions in this file.
> + */
> +#include <linux/string.h>
> +#include <linux/slab.h>
> +#include "lkdtm.h"
Ah, I just noticed one small nit here during build testing: lkdtm.h
needs to be included first to get the correct pr_fmt to avoid a warning:
In file included from drivers/misc/lkdtm/fortify.c:9:
drivers/misc/lkdtm/lkdtm.h:5: warning: "pr_fmt" redefined
5 | #define pr_fmt(fmt) "lkdtm: " fmt
-Kees
--
Kees Cook
