kasan: clean up comments in tests

Clarify and update comments in KASAN tests.

Link: https://linux-review.googlesource.com/id/I6c816c51fa1e0eb7aa3dead6bda1f339d2af46c8
Link: https://lkml.kernel.org/r/ba6db104d53ae0e3796f80ef395f6873c1c1282f.1610733117.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 2947274..6f46e27 100644 (file)
--- 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); \
@@ -121,7 +119,8 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
                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);
@@ -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);
@@ -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);
 }
 
@@ -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));
 
        /*
@@ -585,7 +589,10 @@ 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");
@@ -610,7 +617,10 @@ 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");
@@ -634,7 +644,10 @@ 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");
@@ -706,7 +719,7 @@ static void kasan_bitops_generic(struct kunit *test)
        }
 
        /*
-        * 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);

diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c
index 3b4cc77..eee017f 100644 (file)
--- 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();