[PATCH v2] Add support for stack-protector

Heinrich Schuchardt
2021-01-11T09:59:28Z

On 11.01.21 04:10, Joel Peshkin wrote:
> Cc: Simon Glass <sjg@chromium.org>
> Cc: Bin Meng <bmeng.cn@gmail.com>
> Cc: Jagan Teki <jagan@amarulasolutions.com>
> Cc: Kever Yang <kever.yang@rock-chips.com>
> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
> Cc: Usama Arif <usama.arif@arm.com>
> Cc: Sam Protsenko <joe.skb7@gmail.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Philippe Reynes <philippe.reynes@softathome.com>
> Cc: Eugeniu Rosca <roscaeugeniu@gmail.com>
> Cc: Jan Kiszka <jan.kiszka@siemens.com>
>
> Signed-off-by: Joel Peshkin <joel.peshkin@broadcom.com>
>
> Changes for v2:
> - Add test command and corresponding config
> - Fixed incorrect description in Kconfig
> - Add unit test
> ---
> Makefile | 4 +++
> common/Kconfig | 22 ++++++++++++++
> common/Makefile | 2 ++
> common/stackprot.c | 44 ++++++++++++++++++++++++++++
> configs/sandbox_defconfig | 2 ++
> scripts/Makefile.spl | 6 ++++
> test/py/tests/test_stackprotector.py | 15 ++++++++++
> 7 files changed, 95 insertions(+)
> create mode 100644 common/stackprot.c
> create mode 100644 test/py/tests/test_stackprotector.py
>
> diff --git a/Makefile b/Makefile
> index 3ee4cc00dd..6e7a81ec7d 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -677,7 +677,11 @@ else
> KBUILD_CFLAGS += -O2
> endif
>
> +ifeq ($(CONFIG_STACKPROTECTOR),y)
> +KBUILD_CFLAGS += $(call cc-option,-fstack-protector-strong)
> +else
> KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
> +endif
> KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks)
>
> # disable stringop warnings in gcc 8+
> diff --git a/common/Kconfig b/common/Kconfig
> index 2bce8c9ba1..f773babd3a 100644
> --- a/common/Kconfig
> +++ b/common/Kconfig
> @@ -595,6 +595,28 @@ config TPL_HASH
> and the algorithms it supports are defined in common/hash.c. See
> also CMD_HASH for command-line access.
>
> +config STACKPROTECTOR
> + bool "Stack Protector buffer overflow detection"
> + default n
> + help
> + Enable stack smash detection through gcc built-in stack-protector
> + canary logic
> +
> +config STACKPROTECTOR_TEST_COMMAND

This should be called CMD_STACKPROTECTOR_TEST cmd/Kconfig.

> + bool "Test command for stack protector"
> + depends on STACKPROTECTOR
> + default n
> + help
> + Enable stackprot_test command
> +
> +config SPL_STACKPROTECTOR
> + bool "Stack Protector buffer overflow detection for SPL"

depends on SPL && STACKPROTECTOR

> + default n
> +
> +config TPL_STACKPROTECTOR
> + bool "Stack Protector buffer overflow detection for TPL"

depends on TPL && STACKPROTECTOR

> + default n
> +
> endmenu
>
> menu "Update support"
> diff --git a/common/Makefile b/common/Makefile
> index bcf352d016..fe71e18317 100644
> --- a/common/Makefile
> +++ b/common/Makefile
> @@ -138,3 +138,5 @@ obj-$(CONFIG_CMD_LOADB) += xyzModem.o
> obj-$(CONFIG_$(SPL_TPL_)YMODEM_SUPPORT) += xyzModem.o
>
> obj-$(CONFIG_AVB_VERIFY) += avb_verify.o
> +obj-$(CONFIG_$(SPL_TPL_)STACKPROTECTOR) += stackprot.o
> +
> diff --git a/common/stackprot.c b/common/stackprot.c
> new file mode 100644
> index 0000000000..d602dc7de1
> --- /dev/null
> +++ b/common/stackprot.c
> @@ -0,0 +1,44 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2021 Broadcom
> + */
> +
> +#include <common.h>
> +#include <cli.h>
> +#include <command.h>
> +#include <console.h>
> +
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +unsigned long __stack_chk_guard =
> + (unsigned long)((unsigned long long)0xfeedf00ddeadbeef &
> + ~((unsigned long)0));

Please, use scripts/checkpatch.pl and correct the reported problems, e.g.

WARNING: please, no spaces at the start of a line
#115: FILE: common/stackprot.c:14:
+ (unsigned long)((unsigned long long)0xfeedf00ddeadbeef &$

WARNING: Unnecessary typecast of c90 int constant
#115: FILE: common/stackprot.c:14:
+ (unsigned long)((unsigned long long)0xfeedf00ddeadbeef &

WARNING: Unnecessary typecast of c90 int constant
#116: FILE: common/stackprot.c:15:
+ ~((unsigned long)0));

> +
> +void __stack_chk_fail(void)
> +{
> + panic("Stack smashing detected in function: %p relocated from %p",
> + __builtin_return_address(0),
> + __builtin_return_address(0) - gd->reloc_off);
> +}
> +
> +#ifdef CONFIG_STACKPROTECTOR_TEST_COMMAND

The command should be in directory /cmd/. There you can use the Makefile
to decide if it is compiled.

Please, add a short man-page to /doc/usage/. See doc/usage/button.rst
for a template.

> +static int do_test_stackprot_fail(struct cmd_tbl *cmdtp, int flag, int argc,
> + char *const argv[]);
> +
> +int do_test_stackprot_fail(struct cmd_tbl *cmdtp, int flag, int argc,
> + char *const argv[])
> +{
> + char a[128];
> + char b[256];
> + int i;

Missing empty line.

> + for (i = 0; i < 256; i++) {
> + b[i] = i;
> + }
> + memcpy(a, b, 512);

What is b[] good for? The following seems to be enough to do the test:

{
char a[128];

memset(a, 0xff, 512);
return;
}

Best regards

Heinrich

> + return (0);
> +}
> +
> +U_BOOT_CMD(stackprot_test, 1, 1, do_test_stackprot_fail,
> + "test stack protector fail", "");
> +
> +#endif
> diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
> index f1ec701a9f..da3aca2551 100644
> --- a/configs/sandbox_defconfig
> +++ b/configs/sandbox_defconfig
> @@ -274,3 +274,5 @@ CONFIG_TEST_FDTDEC=y
> CONFIG_UNIT_TEST=y
> CONFIG_UT_TIME=y
> CONFIG_UT_DM=y
> +CONFIG_STACKPROTECTOR=y
> +CONFIG_STACKPROTECTOR_TEST_COMMAND=y
> diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
> index 9f1f7445d7..1505e4e851 100644
> --- a/scripts/Makefile.spl
> +++ b/scripts/Makefile.spl
> @@ -63,6 +63,12 @@ include $(srctree)/scripts/Makefile.lib
> KBUILD_CFLAGS += -ffunction-sections -fdata-sections
> LDFLAGS_FINAL += --gc-sections
>
> +ifeq ($(CONFIG_$(SPL_TPL_)STACKPROTECTOR),y)
> +KBUILD_CFLAGS += -fstack-protector-strong
> +else
> +KBUILD_CFLAGS += -fno-stack-protector
> +endif
> +
> # FIX ME
> cpp_flags := $(KBUILD_CPPFLAGS) $(PLATFORM_CPPFLAGS) $(UBOOTINCLUDE) \
> $(NOSTDINC_FLAGS)
> diff --git a/test/py/tests/test_stackprotector.py b/test/py/tests/test_stackprotector.py
> new file mode 100644
> index 0000000000..49df8eff8c
> --- /dev/null
> +++ b/test/py/tests/test_stackprotector.py
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2021 Broadcom
> +
> +import pytest
> +import signal
> +
> + at pytest.mark.buildconfigspec('stackprotector_test_command')
> +def test_stackprotector(u_boot_console):
> + """Test that the stackprotector function works."""
> +
> + u_boot_console.run_command('stackprot_test',wait_for_prompt=False)
> + expected_response = 'Stack smashing detected'
> + u_boot_console.wait_for(expected_response)
> + assert(True)
> +
>