[PATCH v3] Add support for stack-protector

Joel Peshkin joel.peshkin at broadcom.com
Mon Jan 11 17:20:11 CET 2021 

Cc: Simon Glass <sjg at chromium.org>
Cc: Bin Meng <bmeng.cn at gmail.com>
Cc: Jagan Teki <jagan at amarulasolutions.com>
Cc: Kever Yang <kever.yang at rock-chips.com>
Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
Cc: AKASHI Takahiro <takahiro.akashi at linaro.org>
Cc: Usama Arif <usama.arif at arm.com>
Cc: Sam Protsenko <joe.skb7 at gmail.com>
Cc: Masahiro Yamada <masahiroy at kernel.org>
Cc: Philippe Reynes <philippe.reynes at softathome.com>
Cc: Eugeniu Rosca <roscaeugeniu at gmail.com>
Cc: Jan Kiszka <jan.kiszka at siemens.com>

Signed-off-by: Joel Peshkin <joel.peshkin at broadcom.com>

Changes for v3:
   - Move test command to cmd/
   - Update Kconfig names and depends
   - clean up default canary initialization

Changes for v2:
   - Add test command and corresponding config
   - Fixed incorrect description in Kconfig
   - Add unit test
---
 MAINTAINERS                          |  7 +++++++
 Makefile                             |  4 ++++
 cmd/Kconfig                          | 10 ++++++++++
 cmd/Makefile                         |  1 +
 cmd/stackprot_test.c                 | 26 ++++++++++++++++++++++++++
 common/Kconfig                       | 17 +++++++++++++++++
 common/Makefile                      |  2 ++
 common/stackprot.c                   | 18 ++++++++++++++++++
 configs/sandbox_defconfig            |  2 ++
 scripts/Makefile.spl                 |  6 ++++++
 test/py/tests/test_stackprotector.py | 15 +++++++++++++++
 11 files changed, 108 insertions(+)
 create mode 100644 cmd/stackprot_test.c
 create mode 100644 common/stackprot.c
 create mode 100644 test/py/tests/test_stackprotector.py

diff --git a/MAINTAINERS b/MAINTAINERS
index 52d7307525..2982ffcc07 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1022,6 +1022,13 @@ F:	include/sqfs.h
 F:	cmd/sqfs.c
 F:	test/py/tests/test_fs/test_squashfs/
 
+STACKPROTECTOR
+M:	Joel Peshkin <joel.peshkin at broadcom.com>
+S:	Maintained
+F:	common/stackprot.c
+F:	cmd/stackprot_test.c
+F:	test/py/tests/test_stackprotector.py
+
 TARGET_BCMNS3
 M:	Bharat Gooty <bharat.gooty at broadcom.com>
 M:	Rayagonda Kokatanur <rayagonda.kokatanur at broadcom.com>
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/cmd/Kconfig b/cmd/Kconfig
index 1595de999b..04700e4bb4 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -2271,6 +2271,16 @@ config CMD_AVB
 	    avb read_part_hex - read data from partition and output to stdout
 	    avb write_part - write data to partition
 	    avb verify - run full verification chain
+
+config CMD_STACKPROTECTOR_TEST
+	bool "Test command for stack protector"
+	depends on STACKPROTECTOR
+	default n
+	help
+	  Enable stackprot_test command
+	  The stackprot_test command will force a stack overrun to test
+	  the stack smashing detection mechanisms.
+
 endmenu
 
 config CMD_UBI
diff --git a/cmd/Makefile b/cmd/Makefile
index dd86675bf2..8e8fcea19e 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -142,6 +142,7 @@ obj-$(CONFIG_CMD_SPI) += spi.o
 obj-$(CONFIG_CMD_STRINGS) += strings.o
 obj-$(CONFIG_CMD_SMC) += smccc.o
 obj-$(CONFIG_CMD_SYSBOOT) += sysboot.o pxe_utils.o
+obj-$(CONFIG_CMD_STACKPROTECTOR_TEST) += stackprot_test.o
 obj-$(CONFIG_CMD_TERMINAL) += terminal.o
 obj-$(CONFIG_CMD_TIME) += time.o
 obj-$(CONFIG_CMD_TIMER) += timer.o
diff --git a/cmd/stackprot_test.c b/cmd/stackprot_test.c
new file mode 100644
index 0000000000..ea952c075e
--- /dev/null
+++ b/cmd/stackprot_test.c
@@ -0,0 +1,26 @@
+// 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;
+
+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];
+
+	memset(a, 0xa5, 512);
+	return 0;
+}
+
+U_BOOT_CMD(stackprot_test, 1, 1, do_test_stackprot_fail,
+	   "test stack protector fail", "");
diff --git a/common/Kconfig b/common/Kconfig
index 2bce8c9ba1..5a053c7336 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -595,6 +595,23 @@ 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 SPL_STACKPROTECTOR
+	bool "Stack Protector buffer overflow detection for SPL"
+	depends on STACKPROTECTOR && SPL
+	default n
+
+config TPL_STACKPROTECTOR
+	bool "Stack Protector buffer overflow detection for TPL"
+	depends on STACKPROTECTOR && 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..014257b3e7
--- /dev/null
+++ b/common/stackprot.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  Copyright 2021 Broadcom
+ */
+
+#include <common.h>
+#include <console.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+unsigned long __stack_chk_guard = (long)(0xfeedf00ddeadbeef & ~0L);
+
+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);
+}
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index f1ec701a9f..3e92a58bdb 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_CMD_STACKPROTECTOR_TEST=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..957a2a6cf7
--- /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('cmd_stackprotector_test')
+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

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