[PATCH 03/11] kasan: clean up comments in tests

From: Andrey Konovalov
Date: Tue Jan 05 2021 - 13:29:00 EST

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Clarify and update comments and info messages in KASAN tests.

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Link: https://linux-review.googlesource.com/id/I6c816c51fa1e0eb7aa3dead6bda1f339d2af46c8
---
lib/test_kasan.c | 94 +++++++++++++++++++++++------------------
lib/test_kasan_module.c | 5 ++-
2 files changed, 55 insertions(+), 44 deletions(-)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 2947274cc2d3..46e578c8e842 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -28,10 +28,9 @@
#define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : KASAN_GRANULE_SIZE)

/*
- * We assign some test results to these globals to make sure the tests
- * are not eliminated as dead code.
+ * Some tests use these global variables to store return values from function
+ * calls that could otherwise be eliminated by the compiler as dead code.
*/
-
void *kasan_ptr_result;
int kasan_int_result;

@@ -39,14 +38,13 @@ static struct kunit_resource resource;
static struct kunit_kasan_expectation fail_data;
static bool multishot;

+/*
+ * Temporarily enable multi-shot mode. Otherwise, KASAN would only report the
+ * first detected bug and panic the kernel if panic_on_warn is enabled.
+ */
static int kasan_test_init(struct kunit *test)
{
- /*
- * Temporarily enable multi-shot mode and set panic_on_warn=0.
- * Otherwise, we'd only get a report for the first case.
- */
multishot = kasan_save_enable_multi_shot();
-
return 0;
}

@@ -56,12 +54,12 @@ static void kasan_test_exit(struct kunit *test)
}

/**
- * KUNIT_EXPECT_KASAN_FAIL() - Causes a test failure when the expression does
- * not cause a KASAN error. This uses a KUnit resource named "kasan_data." Do
- * Do not use this name for a KUnit resource outside here.
- *
+ * KUNIT_EXPECT_KASAN_FAIL() - check that the executed expression produces a
+ * KASAN report; causes a test failure otherwise. This relies on a KUnit
+ * resource named "kasan_data". Do not use this name for KUnit resources
+ * outside of KASAN tests.
*/
-#define KUNIT_EXPECT_KASAN_FAIL(test, condition) do { \
+#define KUNIT_EXPECT_KASAN_FAIL(test, expression) do { \
fail_data.report_expected = true; \
fail_data.report_found = false; \
kunit_add_named_resource(test, \
@@ -69,7 +67,7 @@ static void kasan_test_exit(struct kunit *test)
NULL, \
&resource, \
"kasan_data", &fail_data); \
- condition; \
+ expression; \
KUNIT_EXPECT_EQ(test, \
fail_data.report_expected, \
fail_data.report_found); \
@@ -117,11 +115,12 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
size_t size = KMALLOC_MAX_CACHE_SIZE + 10;

if (!IS_ENABLED(CONFIG_SLUB)) {
- kunit_info(test, "CONFIG_SLUB is not enabled.");
+ kunit_info(test, "skipping, CONFIG_SLUB required");
return;
}

- /* Allocate a chunk that does not fit into a SLUB cache to trigger
+ /*
+ * Allocate a chunk that does not fit into a SLUB cache to trigger
* the page allocator fallback.
*/
ptr = kmalloc(size, GFP_KERNEL);
@@ -137,7 +136,7 @@ static void kmalloc_pagealloc_uaf(struct kunit *test)
size_t size = KMALLOC_MAX_CACHE_SIZE + 10;

if (!IS_ENABLED(CONFIG_SLUB)) {
- kunit_info(test, "CONFIG_SLUB is not enabled.");
+ kunit_info(test, "skipping, CONFIG_SLUB required");
return;
}

@@ -154,7 +153,7 @@ static void kmalloc_pagealloc_invalid_free(struct kunit *test)
size_t size = KMALLOC_MAX_CACHE_SIZE + 10;

if (!IS_ENABLED(CONFIG_SLUB)) {
- kunit_info(test, "CONFIG_SLUB is not enabled.");
+ kunit_info(test, "skipping, CONFIG_SLUB required");
return;
}

@@ -168,7 +167,9 @@ static void kmalloc_large_oob_right(struct kunit *test)
{
char *ptr;
size_t size = KMALLOC_MAX_CACHE_SIZE - 256;
- /* Allocate a chunk that is large enough, but still fits into a slab
+
+ /*
+ * Allocate a chunk that is large enough, but still fits into a slab
* and does not trigger the page allocator fallback in SLUB.
*/
ptr = kmalloc(size, GFP_KERNEL);
@@ -218,7 +219,7 @@ static void kmalloc_oob_16(struct kunit *test)

/* This test is specifically crafted for the generic mode. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
- kunit_info(test, "CONFIG_KASAN_GENERIC required\n");
+ kunit_info(test, "skipping, CONFIG_KASAN_GENERIC required");
return;
}

@@ -454,7 +455,7 @@ static void kasan_global_oob(struct kunit *test)

/* Only generic mode instruments globals. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
- kunit_info(test, "CONFIG_KASAN_GENERIC required");
+ kunit_info(test, "skipping, CONFIG_KASAN_GENERIC required");
return;
}

@@ -469,10 +470,13 @@ static void ksize_unpoisons_memory(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
real_size = ksize(ptr);
- /* This access doesn't trigger an error. */
+
+ /* This access shouldn't trigger a KASAN report. */
ptr[size] = 'x';
- /* This one does. */
+
+ /* This one must. */
KUNIT_EXPECT_KASAN_FAIL(test, ptr[real_size] = 'y');
+
kfree(ptr);
}

@@ -483,7 +487,7 @@ static void kasan_stack_oob(struct kunit *test)
char *p = &stack_array[ARRAY_SIZE(stack_array) + i];

if (!IS_ENABLED(CONFIG_KASAN_STACK)) {
- kunit_info(test, "CONFIG_KASAN_STACK is not enabled");
+ kunit_info(test, "skipping, CONFIG_KASAN_STACK required");
return;
}

@@ -498,12 +502,12 @@ static void kasan_alloca_oob_left(struct kunit *test)

/* Only generic mode instruments dynamic allocas. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
- kunit_info(test, "CONFIG_KASAN_GENERIC required");
+ kunit_info(test, "skipping, CONFIG_KASAN_GENERIC required");
return;
}

if (!IS_ENABLED(CONFIG_KASAN_STACK)) {
- kunit_info(test, "CONFIG_KASAN_STACK is not enabled");
+ kunit_info(test, "skipping, CONFIG_KASAN_STACK required");
return;
}

@@ -518,12 +522,12 @@ static void kasan_alloca_oob_right(struct kunit *test)

/* Only generic mode instruments dynamic allocas. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
- kunit_info(test, "CONFIG_KASAN_GENERIC required");
+ kunit_info(test, "skipping, CONFIG_KASAN_GENERIC required");
return;
}

if (!IS_ENABLED(CONFIG_KASAN_STACK)) {
- kunit_info(test, "CONFIG_KASAN_STACK is not enabled");
+ kunit_info(test, "skipping, CONFIG_KASAN_STACK required");
return;
}

@@ -568,7 +572,7 @@ static void kmem_cache_invalid_free(struct kunit *test)
return;
}

- /* Trigger invalid free, the object doesn't get freed */
+ /* Trigger invalid free, the object doesn't get freed. */
KUNIT_EXPECT_KASAN_FAIL(test, kmem_cache_free(cache, p + 1));

/*
@@ -585,10 +589,12 @@ static void kasan_memchr(struct kunit *test)
char *ptr;
size_t size = 24;

- /* See https://bugzilla.kernel.org/show_bug.cgi?id=206337 */
+ /*
+ * str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT.
+ * See https://bugzilla.kernel.org/show_bug.cgi?id=206337 for details.
+ */
if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
- kunit_info(test,
- "str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT");
+ kunit_info(test, "skipping, CONFIG_AMD_MEM_ENCRYPT enabled");
return;
}

@@ -610,10 +616,12 @@ static void kasan_memcmp(struct kunit *test)
size_t size = 24;
int arr[9];

- /* See https://bugzilla.kernel.org/show_bug.cgi?id=206337 */
+ /*
+ * str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT.
+ * See https://bugzilla.kernel.org/show_bug.cgi?id=206337 for details.
+ */
if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
- kunit_info(test,
- "str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT");
+ kunit_info(test, "skipping, CONFIG_AMD_MEM_ENCRYPT enabled");
return;
}

@@ -634,10 +642,12 @@ static void kasan_strings(struct kunit *test)
char *ptr;
size_t size = 24;

- /* See https://bugzilla.kernel.org/show_bug.cgi?id=206337 */
+ /*
+ * str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT.
+ * See https://bugzilla.kernel.org/show_bug.cgi?id=206337 for details.
+ */
if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
- kunit_info(test,
- "str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT");
+ kunit_info(test, "skipping, CONFIG_AMD_MEM_ENCRYPT enabled");
return;
}

@@ -701,12 +711,12 @@ static void kasan_bitops_generic(struct kunit *test)

/* This test is specifically crafted for the generic mode. */
if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
- kunit_info(test, "CONFIG_KASAN_GENERIC required\n");
+ kunit_info(test, "skipping, CONFIG_KASAN_GENERIC required");
return;
}

/*
- * Allocate 1 more byte, which causes kzalloc to round up to 16-bytes;
+ * Allocate 1 more byte, which causes kzalloc to round up to 16 bytes;
* this way we do not actually corrupt other memory.
*/
bits = kzalloc(sizeof(*bits) + 1, GFP_KERNEL);
@@ -733,7 +743,7 @@ static void kasan_bitops_tags(struct kunit *test)

/* This test is specifically crafted for the tag-based mode. */
if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
- kunit_info(test, "CONFIG_KASAN_SW_TAGS required\n");
+ kunit_info(test, "skipping, CONFIG_KASAN_SW_TAGS required");
return;
}

@@ -765,7 +775,7 @@ static void vmalloc_oob(struct kunit *test)
void *area;

if (!IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
- kunit_info(test, "CONFIG_KASAN_VMALLOC is not enabled.");
+ kunit_info(test, "skipping, CONFIG_KASAN_VMALLOC required");
return;
}

diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c
index 3b4cc77992d2..eee017ff8980 100644
--- a/lib/test_kasan_module.c
+++ b/lib/test_kasan_module.c
@@ -123,8 +123,9 @@ static noinline void __init kasan_workqueue_uaf(void)
static int __init test_kasan_module_init(void)
{
/*
- * Temporarily enable multi-shot mode. Otherwise, we'd only get a
- * report for the first case.
+ * Temporarily enable multi-shot mode. Otherwise, KASAN would only
+ * report the first detected bug and panic the kernel if panic_on_warn
+ * is enabled.
*/
bool multishot = kasan_save_enable_multi_shot();

--
2.29.2.729.g45daf8777d-goog

Next message: Andrey Konovalov: "[PATCH 01/11] kasan: prefix exported functions with kasan_"
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In reply to: Andrey Konovalov: "[PATCH 02/11] kasan: clarify HW_TAGS impact on TBI"
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