KASAN-KUnit Integration

This patchset contains everything needed to integrate KASAN and KUnit.

KUnit will be able to:
(1) Fail tests when an unexpected KASAN error occurs
(2) Pass tests when an expected KASAN error occurs

Convert KASAN tests to KUnit with the exception of copy_user_test because KUnit is unable to test those.

Add documentation on how to run the KASAN tests with KUnit and what to expect when running these tests.

The dependencies for this patchset are all present in 5.9-rc1+.

Changes from v12:
- Rebased on top of mainline (ab29a807)
- Updated to match latest KUnit guidelines (no longer rename the test)
- Fix some small issues with the documentation to match the correct test name and mention the module name.

Changes from v11:
- Rebased on top of latest -next (20200810)
- Fixed a redundant memchr() call in kasan_memchr()
- Added Andrey's "Tested-by" to everything.

Changes from v10:
- Fixed some whitespace issues in patch 2.
- Split out the renaming of the KUnit test suite into a separate patch.

Changes from v9:
- Rebased on top of linux-next (20200731) + kselftest/kunit and [7]
- Note that the kasan_rcu_uaf test has not been ported to KUnit, and remains in test_kasan_module. This is because:
(a) KUnit's expect failure will not check if the RCU stacktraces show.
(b) KUnit is unable to link the failure to the test, as it occurs in an RCU callback.

Changes from v8:
- Rebased on top of kselftest/kunit
- (Which, with this patchset, should rebase cleanly on 5.8-rc7)
- Renamed the KUnit test suite, config name to patch the proposed naming guidelines for KUnit tests[6]

Changes from v7:
- Rebased on top of kselftest/kunit
- Rebased on top of v4 of the kunit resources API[1]
- Rebased on top of v4 of the FORTIFY_SOURCE fix[2,3,4]
- Updated the Kconfig entry to support KUNIT_ALL_TESTS

Changes from v6:
- Rebased on top of kselftest/kunit
- Rebased on top of Daniel Axtens' fix for FORTIFY_SOURCE incompatibilites [2]
- Removed a redundant report_enabled() check.
- Fixed some places with out of date Kconfig names in the documentation.

Changes from v5:
- Split out the panic_on_warn changes to a separate patch.
- Fix documentation to fewer to the new Kconfig names.
- Fix some changes which were in the wrong patch.
- Rebase on top of kselftest/kunit (currently identical to 5.7-rc1)

Changes from v4:
- KASAN no longer will panic on errors if both panic_on_warn and kasan_multishot are enabled.
- As a result, the KASAN tests will no-longer disable panic_on_warn.
- This also means panic_on_warn no-longer needs to be exported.
- The use of temporary "kasan_data" variables has been cleaned up somewhat.
- A potential refcount/resource leak should multiple KASAN errors appear during an assertion was fixed.
- Some wording changes to the KASAN test Kconfig entries.

Changes from v3:
- KUNIT_SET_KASAN_DATA and KUNIT_DO_EXPECT_KASAN_FAIL have been combined and included in KUNIT_DO_EXPECT_KASAN_FAIL() instead.
- Reordered logic in kasan_update_kunit_status() in report.c to be easier to read.
- Added comment to not use the name "kasan_data" for any kunit tests outside of KUNIT_EXPECT_KASAN_FAIL().

Changes since v2:
- Due to Alan's changes in [1], KUnit can be built as a module.
- The name of the tests that could not be run with KUnit has been changed to be more generic: test_kasan_module.
- Documentation on how to run the new KASAN tests and what to expect when running them has been added.
- Some variables and functions are now static.
- Now save/restore panic_on_warn in a similar way to kasan_multi_shot and renamed the init/exit functions to be more generic to accommodate.
- Due to [4] in kasan_strings, kasan_memchr, and kasan_memcmp will fail if CONFIG_AMD_MEM_ENCRYPT is enabled so return early and print message explaining this circumstance.
- Changed preprocessor checks to C checks where applicable.

Changes since v1:
- Make use of Alan Maguire's suggestion to use his patch that allows static resources for integration instead of adding a new attribute to the kunit struct
- All KUNIT_EXPECT_KASAN_FAIL statements are local to each test
- The definition of KUNIT_EXPECT_KASAN_FAIL is local to the test_kasan.c file since it seems this is the only place this will be used.
- Integration relies on KUnit being builtin
- copy_user_test has been separated into its own file since KUnit is unable to test these. This can be run as a module just as before, using CONFIG_TEST_KASAN_USER
- The addition to the current task has been separated into its own patch as this is a significant enough change to be on its own.

[1] https://lore.kernel.org/linux-kselftest/CAFd5g46Uu_5TG89uOm0Dj5CMq+11cwjBnsd-k_CVy6bQUeU4Jw@mail.gmail.com/T/#t
[2] https://lore.kernel.org/linux-mm/[email protected]/
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=adb72ae1915db28f934e9e02c18bfcea2f3ed3b7
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=47227d27e2fcb01a9e8f5958d8997cf47a820afc
[5] https://bugzilla.kernel.org/show_bug.cgi?id=206337
[6] https://lore.kernel.org/linux-kselftest/[email protected]/
[7] https://lkml.org/lkml/2020/7/31/571
[8] https://lore.kernel.org/linux-kselftest/[email protected]/T/#u

David Gow (1):
mm: kasan: Do not panic if both panic_on_warn and kasan_multishot set

Patricia Alfonso (4):
Add KUnit Struct to Current Task
KUnit: KASAN Integration

  KASAN: Port KASAN Tests to KUnit
  KASAN: Testing Documentation

 Documentation/dev-tools/kasan.rst |  70 +++
 include/kunit/test.h              |   5 +
 include/linux/kasan.h             |   6 +
 include/linux/sched.h             |   4 +
 lib/Kconfig.kasan                 |  22 +-
 lib/Makefile                      |   3 +-
 lib/kunit/test.c                  |  13 +-
 lib/test_kasan.c                  | 728 ++++++++++++------------------
 lib/test_kasan_module.c           | 111 +++++
 mm/kasan/report.c                 |  34 +-
 10 files changed, 553 insertions(+), 443 deletions(-)
 create mode 100644 lib/test_kasan_module.c

2.28.0.526.ge36021eeef-goog

From: Patricia Alfonso <[email protected]>

In order to integrate debugging tools like KASAN into the KUnit framework, add KUnit struct to the current task to keep track of the current KUnit test.

---
 include/linux/sched.h | 4 ++++
 1 file changed, 4 insertions(+)

index afe01e232935..9df9416c5a40 100644
@@ -1203,6 +1203,10 @@ struct task_struct {
 #endif
 #endif
 
+#if IS_ENABLED(CONFIG_KUNIT)
+	struct kunit			*kunit_test;
+#endif
+
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	/* Index of current stored address in ret_stack: */
 	int				curr_ret_stack;

2.28.0.526.ge36021eeef-goog

From: Patricia Alfonso <[email protected]>

Integrate KASAN into KUnit testing framework.
- Fail tests when KASAN reports an error that is not expected
- Use KUNIT_EXPECT_KASAN_FAIL to expect a KASAN error in KASAN tests
- Expected KASAN reports pass tests and are still printed when run without kunit_tool (kunit_tool still bypasses the report due to the test passing)
- KUnit struct in current task used to keep track of the current test from KASAN code

Make use of "[PATCH v3 kunit-next 1/2] kunit: generalize kunit_resource API beyond allocated resources" and "[PATCH v3 kunit-next 2/2] kunit: add support for named resources" from Alan Maguire [1]
- A named resource is added to a test when a KASAN report is expected
- This resource contains a struct for kasan_data containing booleans representing if a KASAN report is expected and if a KASAN report is found

[1] (https://lore.kernel.org/linux-kselftest/[email protected]/T/#t)

---
 include/kunit/test.h  |  5 +++++
 include/linux/kasan.h |  6 ++++++
 lib/kunit/test.c      | 13 +++++++-----
 lib/test_kasan.c      | 47 +++++++++++++++++++++++++++++++++++++++++--
 mm/kasan/report.c     | 32 +++++++++++++++++++++++++++++
 5 files changed, 96 insertions(+), 7 deletions(-)

index 59f3144f009a..3391f38389f8 100644
@@ -224,6 +224,11 @@ struct kunit {
 	struct list_head resources; /* Protected by lock. */
 };
 
+static inline void kunit_set_failure(struct kunit *test)
+{
+	WRITE_ONCE(test->success, false);
+}
+
 void kunit_init_test(struct kunit *test, const char *name, char *log);
 
 int kunit_run_tests(struct kunit_suite *suite);

index 087fba34b209..30d343b4a40a 100644
@@ -14,6 +14,12 @@ struct task_struct;
 #include <linux/pgtable.h>
 #include <asm/kasan.h>
 
+/* kasan_data struct is used in KUnit tests for KASAN expected failures */
+struct kunit_kasan_expectation {
+	bool report_expected;
+	bool report_found;
+};
+
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
 extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
 extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];

index c36037200310..dcc35fd30d95 100644
@@ -10,16 +10,12 @@
 #include <linux/kernel.h>
 #include <linux/kref.h>
 #include <linux/sched/debug.h>
+#include <linux/sched.h>
 
 #include "debugfs.h"
 #include "string-stream.h"
 #include "try-catch-impl.h"
 
-static void kunit_set_failure(struct kunit *test)
-{
-	WRITE_ONCE(test->success, false);
-}
-
 static void kunit_print_tap_version(void)
 {
 	static bool kunit_has_printed_tap_version;

@@ -288,6 +284,10 @@ static void kunit_try_run_case(void *data)
 	struct kunit_suite *suite = ctx->suite;
 	struct kunit_case *test_case = ctx->test_case;
 
+#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
+	current->kunit_test = test;
+#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT) */
+
 	/*
 	 * kunit_run_case_internal may encounter a fatal error; if it does,
 	 * abort will be called, this thread will exit, and finally the parent

@@ -602,6 +602,9 @@ void kunit_cleanup(struct kunit *test)
 		spin_unlock(&test->lock);
 		kunit_remove_resource(test, res);
 	}
+#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
+	current->kunit_test = NULL;
+#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT)*/
 }
 EXPORT_SYMBOL_GPL(kunit_cleanup);
 

index 4f49fa6cd1aa..e2c14b10bc81 100644
@@ -33,6 +33,8 @@
 
 #include <asm/sections.h>
 
+#include <kunit/test.h>
+
 #include "kasan.h"
 #include "../slab.h"
 

@@ -464,12 +466,37 @@ static bool report_enabled(void)
 	return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 }
 
+#if IS_ENABLED(CONFIG_KUNIT)
+static void kasan_update_kunit_status(struct kunit *cur_test)
+{
+	struct kunit_resource *resource;
+	struct kunit_kasan_expectation *kasan_data;
+
+	resource = kunit_find_named_resource(cur_test, "kasan_data");
+
+	if (!resource) {
+		kunit_set_failure(cur_test);
+		return;
+	}
+
+	kasan_data = (struct kunit_kasan_expectation *)resource->data;
+	kasan_data->report_found = true;
+	kunit_put_resource(resource);
+}
+#endif /* IS_ENABLED(CONFIG_KUNIT) */
+
 void kasan_report_invalid_free(void *object, unsigned long ip)
 {
 	unsigned long flags;
 	u8 tag = get_tag(object);
 
 	object = reset_tag(object);
+
+#if IS_ENABLED(CONFIG_KUNIT)
+	if (current->kunit_test)
+		kasan_update_kunit_status(current->kunit_test);
+#endif /* IS_ENABLED(CONFIG_KUNIT) */
+
 	start_report(&flags);
 	pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 	print_tags(tag, object);

@@ -488,6 +515,11 @@ static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 	void *untagged_addr;
 	unsigned long flags;
 
+#if IS_ENABLED(CONFIG_KUNIT)
+	if (current->kunit_test)
+		kasan_update_kunit_status(current->kunit_test);
+#endif /* IS_ENABLED(CONFIG_KUNIT) */
+
 	disable_trace_on_warning();
 
 	tagged_addr = (void *)addr;

2.28.0.526.ge36021eeef-goog

From: Patricia Alfonso <[email protected]>

Transfer all previous tests for KASAN to KUnit so they can be run more easily. Using kunit_tool, developers can run these tests with their other KUnit tests and see "pass" or "fail" with the appropriate KASAN report instead of needing to parse each KASAN report to test KASAN functionalities. All KASAN reports are still printed to dmesg.

Stack tests do not work properly when KASAN_STACK is enabled so those tests use a check for "if IS_ENABLED(CONFIG_KASAN_STACK)" so they only run if stack instrumentation is enabled. If KASAN_STACK is not enabled, KUnit will print a statement to let the user know this test was not run with KASAN_STACK enabled.

copy_user_test and kasan_rcu_uaf cannot be run in KUnit so there is a separate test file for those tests, which can be run as before as a module.

---
 lib/Kconfig.kasan       |  22 +-
 lib/Makefile            |   3 +-
 lib/test_kasan.c        | 687 +++++++++++++++-------------------------
 lib/test_kasan_module.c | 111 +++++++
 4 files changed, 385 insertions(+), 438 deletions(-)
 create mode 100644 lib/test_kasan_module.c

index 047b53dbfd58..9a237887e52e 100644
@@ -167,12 +167,24 @@ config KASAN_VMALLOC
 	  for KASAN to detect more sorts of errors (and to support vmapped
 	  stacks), but at the cost of higher memory usage.
 
-config TEST_KASAN
-	tristate "Module for testing KASAN for bug detection"
-	depends on m
+config KASAN_KUNIT_TEST
+	tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS
+	depends on KASAN && KUNIT
+	default KUNIT_ALL_TESTS
 	help
-	  This is a test module doing various nasty things like
-	  out of bounds accesses, use after free. It is useful for testing
+	  This is a KUnit test suite doing various nasty things like
+	  out of bounds and use after free accesses. It is useful for testing
 	  kernel debugging features like KASAN.
 
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit
+
+config TEST_KASAN_MODULE
+	tristate "KUnit-incompatible tests of KASAN bug detection capabilities"
+	depends on m && KASAN
+	help
+	  This is a part of the KASAN test suite that is incompatible with
+	  KUnit. Currently includes tests that do bad copy_from/to_user
+	  accesses.
+
 endif # KASAN

index a4a4c6864f51..8c94cad26db7 100644
@@ -65,9 +65,10 @@ CFLAGS_test_bitops.o += -Werror
 obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o
 obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o
 obj-$(CONFIG_TEST_IDA) += test_ida.o
-obj-$(CONFIG_TEST_KASAN) += test_kasan.o
+obj-$(CONFIG_KASAN_KUNIT_TEST) += test_kasan.o
 CFLAGS_test_kasan.o += -fno-builtin
 CFLAGS_test_kasan.o += $(call cc-disable-warning, vla)
+obj-$(CONFIG_TEST_KASAN_MODULE) += test_kasan_module.o
 obj-$(CONFIG_TEST_UBSAN) += test_ubsan.o
 CFLAGS_test_ubsan.o += $(call cc-disable-warning, vla)
 UBSAN_SANITIZE_test_ubsan.o := y

2.28.0.526.ge36021eeef-goog

From: Patricia Alfonso <[email protected]>

Include documentation on how to test KASAN using CONFIG_TEST_KASAN_KUNIT and CONFIG_TEST_KASAN_MODULE.

---
 Documentation/dev-tools/kasan.rst | 70 +++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

index 38fd5681fade..072ecdadba07 100644
@@ -281,3 +281,73 @@ unmapped. This will require changes in arch-specific code.
 
 This allows ``VMAP_STACK`` support on x86, and can simplify support of
 architectures that do not have a fixed module region.
+
+CONFIG_KASAN_KUNIT_TEST & CONFIG_TEST_KASAN_MODULE
+--------------------------------------------------
+
+``CONFIG_KASAN_KUNIT_TEST`` utilizes the KUnit Test Framework for testing.
+This means each test focuses on a small unit of functionality and
+there are a few ways these tests can be run.
+
+Each test will print the KASAN report if an error is detected and then
+print the number of the test and the status of the test:
+
+pass::
+
+        ok 28 - kmalloc_double_kzfree
+or, if kmalloc failed::
+
+        # kmalloc_large_oob_right: ASSERTION FAILED at lib/test_kasan.c:163
+        Expected ptr is not null, but is
+        not ok 4 - kmalloc_large_oob_right
+or, if a KASAN report was expected, but not found::
+
+        # kmalloc_double_kzfree: EXPECTATION FAILED at lib/test_kasan.c:629
+        Expected kasan_data->report_expected == kasan_data->report_found, but
+        kasan_data->report_expected == 1
+        kasan_data->report_found == 0
+        not ok 28 - kmalloc_double_kzfree
+
+All test statuses are tracked as they run and an overall status will
+be printed at the end::
+
+        ok 1 - kasan
+
+or::
+
+        not ok 1 - kasan
+
+(1) Loadable Module
+~~~~~~~~~~~~~~~~~~~~
+
+With ``CONFIG_KUNIT`` enabled, ``CONFIG_KASAN_KUNIT_TEST`` can be built as
+a loadable module and run on any architecture that supports KASAN
+using something like insmod or modprobe. The module is called ``test_kasan``.
+
+(2) Built-In
+~~~~~~~~~~~~~
+
+With ``CONFIG_KUNIT`` built-in, ``CONFIG_KASAN_KUNIT_TEST`` can be built-in
+on any architecure that supports KASAN. These and any other KUnit
+tests enabled will run and print the results at boot as a late-init
+call.
+
+(3) Using kunit_tool
+~~~~~~~~~~~~~~~~~~~~~
+
+With ``CONFIG_KUNIT`` and ``CONFIG_KASAN_KUNIT_TEST`` built-in, we can also
+use kunit_tool to see the results of these along with other KUnit
+tests in a more readable way. This will not print the KASAN reports
+of tests that passed. Use `KUnit documentation <https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html>`_ for more up-to-date
+information on kunit_tool.
+
+.. _KUnit: https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html
+
+``CONFIG_TEST_KASAN_MODULE`` is a set of KASAN tests that could not be
+converted to KUnit. These tests can be run only as a module with
+``CONFIG_TEST_KASAN_MODULE`` built as a loadable module and
+``CONFIG_KASAN`` built-in. The type of error expected and the
+function being run is printed before the expression expected to give
+an error. Then the error is printed, if found, and that test
+should be interpretted to pass only if the error was the one expected
+by the test.

2.28.0.526.ge36021eeef-goog

KASAN errors will currently trigger a panic when panic_on_warn is set. This renders kasan_multishot useless, as further KASAN errors won't be reported if the kernel has already paniced. By making kasan_multishot disable this behaviour for KASAN errors, we can still have the benefits of panic_on_warn for non-KASAN warnings, yet be able to use kasan_multishot.

This is particularly important when running KASAN tests, which need to trigger multiple KASAN errors: previously these would panic the system if panic_on_warn was set, now they can run (and will panic the system should non-KASAN warnings show up).

---
 mm/kasan/report.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index e2c14b10bc81..00a53f1355ae 100644
@@ -95,7 +95,7 @@ static void end_report(unsigned long *flags)
 	pr_err("==================================================================\n");
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 	spin_unlock_irqrestore(&report_lock, *flags);
-	if (panic_on_warn) {
+	if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
 		/*
 		 * This thread may hit another WARN() in the panic path.
 		 * Resetting this prevents additional WARN() from panicking the

2.28.0.526.ge36021eeef-goog

Hi Andrew,

Could you consider taking this for 5.10?

Thanks!