[PATCH v2 32/63] fortify: Add compile-time FORTIFY_SOURCE tests

Kees Cook
2021-08-18T06:24:39Z

While the run-time testing of FORTIFY_SOURCE is already present in
LKDTM, there is no testing of the expected compile-time detections. In
preparation for correctly supporting FORTIFY_SOURCE under Clang, adding
additional FORTIFY_SOURCE defenses, and making sure FORTIFY_SOURCE
doesn't silently regress with GCC, introduce a build-time test suite that
checks each expected compile-time failure condition.

As this is relatively backwards from standard build rules in the
sense that a successful test is actually a compile _failure_, create
a wrapper script to check for the correct errors, and wire it up as
a dummy dependency to lib/string.o, collecting the results into a log
file artifact.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
lib/.gitignore | 2 +
lib/Makefile | 33 +++++++++++
lib/test_fortify/read_overflow-memchr.c | 5 ++
lib/test_fortify/read_overflow-memchr_inv.c | 5 ++
lib/test_fortify/read_overflow-memcmp.c | 5 ++
lib/test_fortify/read_overflow-memscan.c | 5 ++
lib/test_fortify/read_overflow2-memcmp.c | 5 ++
lib/test_fortify/read_overflow2-memcpy.c | 5 ++
lib/test_fortify/read_overflow2-memmove.c | 5 ++
lib/test_fortify/test_fortify.h | 35 +++++++++++
lib/test_fortify/write_overflow-memcpy.c | 5 ++
lib/test_fortify/write_overflow-memmove.c | 5 ++
lib/test_fortify/write_overflow-memset.c | 5 ++
lib/test_fortify/write_overflow-strcpy-lit.c | 5 ++
lib/test_fortify/write_overflow-strcpy.c | 5 ++
lib/test_fortify/write_overflow-strlcpy-src.c | 5 ++
lib/test_fortify/write_overflow-strlcpy.c | 5 ++
lib/test_fortify/write_overflow-strncpy-src.c | 5 ++
lib/test_fortify/write_overflow-strncpy.c | 5 ++
lib/test_fortify/write_overflow-strscpy.c | 5 ++
scripts/test_fortify.sh | 59 +++++++++++++++++++
21 files changed, 214 insertions(+)
create mode 100644 lib/test_fortify/read_overflow-memchr.c
create mode 100644 lib/test_fortify/read_overflow-memchr_inv.c
create mode 100644 lib/test_fortify/read_overflow-memcmp.c
create mode 100644 lib/test_fortify/read_overflow-memscan.c
create mode 100644 lib/test_fortify/read_overflow2-memcmp.c
create mode 100644 lib/test_fortify/read_overflow2-memcpy.c
create mode 100644 lib/test_fortify/read_overflow2-memmove.c
create mode 100644 lib/test_fortify/test_fortify.h
create mode 100644 lib/test_fortify/write_overflow-memcpy.c
create mode 100644 lib/test_fortify/write_overflow-memmove.c
create mode 100644 lib/test_fortify/write_overflow-memset.c
create mode 100644 lib/test_fortify/write_overflow-strcpy-lit.c
create mode 100644 lib/test_fortify/write_overflow-strcpy.c
create mode 100644 lib/test_fortify/write_overflow-strlcpy-src.c
create mode 100644 lib/test_fortify/write_overflow-strlcpy.c
create mode 100644 lib/test_fortify/write_overflow-strncpy-src.c
create mode 100644 lib/test_fortify/write_overflow-strncpy.c
create mode 100644 lib/test_fortify/write_overflow-strscpy.c
create mode 100644 scripts/test_fortify.sh

diff --git a/lib/.gitignore b/lib/.gitignore
index 5e7fa54c4536..e5e217b8307b 100644
--- a/lib/.gitignore
+++ b/lib/.gitignore
@@ -4,3 +4,5 @@
/gen_crc32table
/gen_crc64table
/oid_registry_data.c
+/test_fortify.log
+/test_fortify/*.log
diff --git a/lib/Makefile b/lib/Makefile
index 5efd1b435a37..bd17c2bf43e1 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -360,3 +360,36 @@ obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o
obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o

obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
+
+# FORTIFY_SOURCE compile-time behavior tests
+TEST_FORTIFY_SRCS = $(wildcard $(srctree)/$(src)/test_fortify/*-*.c)
+TEST_FORTIFY_LOGS = $(patsubst $(srctree)/$(src)/%.c, %.log, $(TEST_FORTIFY_SRCS))
+TEST_FORTIFY_LOG = test_fortify.log
+
+quiet_cmd_test_fortify = TEST $@
+ cmd_test_fortify = $(CONFIG_SHELL) $(srctree)/scripts/test_fortify.sh \
+ $< $@ "$(NM)" $(CC) $(c_flags) \
+ $(call cc-disable-warning,fortify-source)
+
+targets += $(TEST_FORTIFY_LOGS)
+clean-files += $(TEST_FORTIFY_LOGS)
+clean-files += $(addsuffix .o, $(TEST_FORTIFY_LOGS))
+$(obj)/test_fortify/%.log: $(src)/test_fortify/%.c \
+ $(src)/test_fortify/test_fortify.h \
+ $(srctree)/include/linux/fortify-string.h \
+ $(srctree)/scripts/test_fortify.sh \
+ FORCE
+ $(call if_changed,test_fortify)
+
+quiet_cmd_gen_fortify_log = GEN $@
+ cmd_gen_fortify_log = cat </dev/null $(filter-out FORCE,$^) 2>/dev/null > $@ || true
+
+targets += $(TEST_FORTIFY_LOG)
+clean-files += $(TEST_FORTIFY_LOG)
+$(obj)/$(TEST_FORTIFY_LOG): $(addprefix $(obj)/, $(TEST_FORTIFY_LOGS)) FORCE
+ $(call if_changed,gen_fortify_log)
+
+# Fake dependency to trigger the fortify tests.
+ifeq ($(CONFIG_FORTIFY_SOURCE),y)
+$(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)
+endif
diff --git a/lib/test_fortify/read_overflow-memchr.c b/lib/test_fortify/read_overflow-memchr.c
new file mode 100644
index 000000000000..2743084b32af
--- /dev/null
+++ b/lib/test_fortify/read_overflow-memchr.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memchr(small, 0x7A, sizeof(small) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/read_overflow-memchr_inv.c b/lib/test_fortify/read_overflow-memchr_inv.c
new file mode 100644
index 000000000000..b26e1f1bc217
--- /dev/null
+++ b/lib/test_fortify/read_overflow-memchr_inv.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memchr_inv(small, 0x7A, sizeof(small) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/read_overflow-memcmp.c b/lib/test_fortify/read_overflow-memcmp.c
new file mode 100644
index 000000000000..d5d301ff64ef
--- /dev/null
+++ b/lib/test_fortify/read_overflow-memcmp.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memcmp(small, large, sizeof(small) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/read_overflow-memscan.c b/lib/test_fortify/read_overflow-memscan.c
new file mode 100644
index 000000000000..c1a97f2df0f0
--- /dev/null
+++ b/lib/test_fortify/read_overflow-memscan.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memscan(small, 0x7A, sizeof(small) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/read_overflow2-memcmp.c b/lib/test_fortify/read_overflow2-memcmp.c
new file mode 100644
index 000000000000..c6091e640f76
--- /dev/null
+++ b/lib/test_fortify/read_overflow2-memcmp.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memcmp(large, small, sizeof(small) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/read_overflow2-memcpy.c b/lib/test_fortify/read_overflow2-memcpy.c
new file mode 100644
index 000000000000..07b62e56cf16
--- /dev/null
+++ b/lib/test_fortify/read_overflow2-memcpy.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memcpy(large, instance.buf, sizeof(large))
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/read_overflow2-memmove.c b/lib/test_fortify/read_overflow2-memmove.c
new file mode 100644
index 000000000000..34edfab040a3
--- /dev/null
+++ b/lib/test_fortify/read_overflow2-memmove.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memmove(large, instance.buf, sizeof(large))
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/test_fortify.h b/lib/test_fortify/test_fortify.h
new file mode 100644
index 000000000000..e1dfe64d79a3
--- /dev/null
+++ b/lib/test_fortify/test_fortify.h
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+void do_fortify_tests(void);
+
+#define __BUF_SMALL 16
+#define __BUF_LARGE 32
+struct fortify_object {
+ int a;
+ char buf[__BUF_SMALL];
+ int c;
+};
+
+#define LITERAL_SMALL "AAAAAAAAAAAAAAA"
+#define LITERAL_LARGE "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
+const char small_src[__BUF_SMALL] = LITERAL_SMALL;
+const char large_src[__BUF_LARGE] = LITERAL_LARGE;
+
+char small[__BUF_SMALL];
+char large[__BUF_LARGE];
+struct fortify_object instance;
+size_t size;
+
+void do_fortify_tests(void)
+{
+ /* Normal initializations. */
+ memset(&instance, 0x32, sizeof(instance));
+ memset(small, 0xA5, sizeof(small));
+ memset(large, 0x5A, sizeof(large));
+
+ TEST;
+}
diff --git a/lib/test_fortify/write_overflow-memcpy.c b/lib/test_fortify/write_overflow-memcpy.c
new file mode 100644
index 000000000000..3b3984e428fb
--- /dev/null
+++ b/lib/test_fortify/write_overflow-memcpy.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memcpy(instance.buf, large_src, sizeof(large_src))
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-memmove.c b/lib/test_fortify/write_overflow-memmove.c
new file mode 100644
index 000000000000..640437c3b3e0
--- /dev/null
+++ b/lib/test_fortify/write_overflow-memmove.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memmove(instance.buf, large_src, sizeof(large_src))
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-memset.c b/lib/test_fortify/write_overflow-memset.c
new file mode 100644
index 000000000000..36e34908cfb3
--- /dev/null
+++ b/lib/test_fortify/write_overflow-memset.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ memset(instance.buf, 0x5A, sizeof(large_src))
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-strcpy-lit.c b/lib/test_fortify/write_overflow-strcpy-lit.c
new file mode 100644
index 000000000000..51effb3e50f9
--- /dev/null
+++ b/lib/test_fortify/write_overflow-strcpy-lit.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ strcpy(small, LITERAL_LARGE)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-strcpy.c b/lib/test_fortify/write_overflow-strcpy.c
new file mode 100644
index 000000000000..84f1c56a64c8
--- /dev/null
+++ b/lib/test_fortify/write_overflow-strcpy.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ strcpy(small, large_src)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-strlcpy-src.c b/lib/test_fortify/write_overflow-strlcpy-src.c
new file mode 100644
index 000000000000..91bf83ebd34a
--- /dev/null
+++ b/lib/test_fortify/write_overflow-strlcpy-src.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ strlcpy(small, large_src, sizeof(small) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-strlcpy.c b/lib/test_fortify/write_overflow-strlcpy.c
new file mode 100644
index 000000000000..1883db7c0cd6
--- /dev/null
+++ b/lib/test_fortify/write_overflow-strlcpy.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ strlcpy(instance.buf, large_src, sizeof(instance.buf) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-strncpy-src.c b/lib/test_fortify/write_overflow-strncpy-src.c
new file mode 100644
index 000000000000..8dcfb8c788dd
--- /dev/null
+++ b/lib/test_fortify/write_overflow-strncpy-src.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ strncpy(small, large_src, sizeof(small) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-strncpy.c b/lib/test_fortify/write_overflow-strncpy.c
new file mode 100644
index 000000000000..b85f079c815d
--- /dev/null
+++ b/lib/test_fortify/write_overflow-strncpy.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ strncpy(instance.buf, large_src, sizeof(instance.buf) + 1)
+
+#include "test_fortify.h"
diff --git a/lib/test_fortify/write_overflow-strscpy.c b/lib/test_fortify/write_overflow-strscpy.c
new file mode 100644
index 000000000000..38feddf377dc
--- /dev/null
+++ b/lib/test_fortify/write_overflow-strscpy.c
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define TEST \
+ strscpy(instance.buf, large_src, sizeof(instance.buf) + 1)
+
+#include "test_fortify.h"
diff --git a/scripts/test_fortify.sh b/scripts/test_fortify.sh
new file mode 100644
index 000000000000..a6d63871738b
--- /dev/null
+++ b/scripts/test_fortify.sh
@@ -0,0 +1,59 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+set -e
+
+# Argument 1: Source file to build.
+IN="$1"
+shift
+# Extract just the filename for error messages below.
+FILE="${IN##*/}"
+# Extract the function name for error messages below.
+FUNC="${FILE#*-}"
+FUNC="${FUNC%%-*}"
+FUNC="${FUNC%%.*}"
+# Extract the symbol to test for in build/symbol test below.
+WANT="__${FILE%%-*}"
+
+# Argument 2: Where to write the build log.
+OUT="$1"
+shift
+TMP="${OUT}.tmp"
+
+# Argument 3: Path to "nm" tool.
+NM="$1"
+shift
+
+# Remaining arguments are: $(CC) $(c_flags)
+
+# Clean up temporary file at exit.
+__cleanup() {
+ rm -f "$TMP"
+}
+trap __cleanup EXIT
+
+status=
+# Attempt to build a source that is expected to fail with a specific warning.
+if "$@" -Werror -c "$IN" -o "$OUT".o 2> "$TMP" ; then
+ # If the build succeeds, either the test has failed or the the
+ # warning may only happen at link time (Clang). In that case,
+ # make sure the expected symbol is unresolved in the symbol list.
+ # If so, FORTIFY is working for this case.
+ if ! $NM -A "$OUT".o | grep -m1 "\bU ${WANT}$" >>"$TMP" ; then
+ status="warning: unsafe ${FUNC}() usage lacked '$WANT' symbol in $IN"
+ fi
+else
+ # If the build failed, check for the warning in the stderr (gcc).
+ if ! grep -q -m1 "error:.*\b${WANT}'" "$TMP" ; then
+ status="warning: unsafe ${FUNC}() usage lacked '$WANT' warning in $IN"
+ fi
+fi
+
+if [ -n "$status" ]; then
+ # Report on failure results, including compilation warnings.
+ echo "$status" | tee "$OUT" >&2
+ cat "$TMP" | tee -a "$OUT" >&2
+else
+ # Report on good results, and save any compilation output to log.
+ echo "ok: unsafe ${FUNC}() usage correctly detected with '$WANT' in $IN" >"$OUT"
+ cat "$TMP" >>"$OUT"
+fi
--
2.30.2