[PATCH v2] Add support for stack-protector

Joel Peshkin
2021-01-11T03:10:52Z

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
+ 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"
+ default n
+
+config TPL_STACKPROTECTOR
+ bool "Stack Protector buffer overflow detection for TPL"
+ 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));
+
+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
+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;
+ for (i = 0; i < 256; i++) {
+ b[i] = i;
+ }
+ memcpy(a, b, 512);
+ 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
+
+@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)
+
--
2.27.0