kasan: support kasan.stacktrace for SW_TAGS

Add support for the kasan.stacktrace command-line argument for Software
Tag-Based KASAN.

The following patch adds a command-line argument for selecting the stack
ring size, and, as the stack ring is supported by both the Software and
the Hardware Tag-Based KASAN modes, it is natural that both of them have
support for kasan.stacktrace too.

Link: https://lkml.kernel.org/r/3b43059103faa7f8796017847b7d674b658f11b5.1662411799.git.andreyknvl@google.comSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/dev-tools/kasan.rst

@@ -111,9 +111,15 @@ parameter can be used to control panic and reporting behaviour:
   report or also panic the kernel (default: ``report``). The panic happens even
   if ``kasan_multi_shot`` is enabled.
 
-Hardware Tag-Based KASAN mode (see the section about various modes below) is
-intended for use in production as a security mitigation. Therefore, it supports
-additional boot parameters that allow disabling KASAN or controlling features:
+Software and Hardware Tag-Based KASAN modes (see the section about various
+modes below) support disabling stack trace collection:
+
+- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
+  traces collection (default: ``on``).
+
+Hardware Tag-Based KASAN mode is intended for use in production as a security
+mitigation. Therefore, it supports additional boot parameters that allow
+disabling KASAN altogether or controlling its features:
 
 - ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
 
@@ -132,9 +138,6 @@ additional boot parameters that allow disabling KASAN or controlling features:
 - ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc
   allocations (default: ``on``).
 
-- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
-  traces collection (default: ``on``).
-
 Error reports
 ~~~~~~~~~~~~~
 

mm/kasan/hw_tags.c

@@ -38,16 +38,9 @@ enum kasan_arg_vmalloc {
 	KASAN_ARG_VMALLOC_ON,
 };
 
-enum kasan_arg_stacktrace {
-	KASAN_ARG_STACKTRACE_DEFAULT,
-	KASAN_ARG_STACKTRACE_OFF,
-	KASAN_ARG_STACKTRACE_ON,
-};
-
 static enum kasan_arg kasan_arg __ro_after_init;
 static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
 static enum kasan_arg_vmalloc kasan_arg_vmalloc __initdata;
-static enum kasan_arg_stacktrace kasan_arg_stacktrace __initdata;
 
 /*
  * Whether KASAN is enabled at all.
@@ -66,9 +59,6 @@ EXPORT_SYMBOL_GPL(kasan_mode);
 /* Whether to enable vmalloc tagging. */
 DEFINE_STATIC_KEY_TRUE(kasan_flag_vmalloc);
 
-/* Whether to collect alloc/free stack traces. */
-DEFINE_STATIC_KEY_TRUE(kasan_flag_stacktrace);
-
 /* kasan=off/on */
 static int __init early_kasan_flag(char *arg)
 {
@@ -122,23 +112,6 @@ static int __init early_kasan_flag_vmalloc(char *arg)
 }
 early_param("kasan.vmalloc", early_kasan_flag_vmalloc);
 
-/* kasan.stacktrace=off/on */
-static int __init early_kasan_flag_stacktrace(char *arg)
-{
-	if (!arg)
-		return -EINVAL;
-
-	if (!strcmp(arg, "off"))
-		kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
-	else if (!strcmp(arg, "on"))
-		kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
-	else
-		return -EINVAL;
-
-	return 0;
-}
-early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
-
 static inline const char *kasan_mode_info(void)
 {
 	if (kasan_mode == KASAN_MODE_ASYNC)
@@ -213,17 +186,7 @@ void __init kasan_init_hw_tags(void)
 		break;
 	}
 
-	switch (kasan_arg_stacktrace) {
-	case KASAN_ARG_STACKTRACE_DEFAULT:
-		/* Default is specified by kasan_flag_stacktrace definition. */
-		break;
-	case KASAN_ARG_STACKTRACE_OFF:
-		static_branch_disable(&kasan_flag_stacktrace);
-		break;
-	case KASAN_ARG_STACKTRACE_ON:
-		static_branch_enable(&kasan_flag_stacktrace);
-		break;
-	}
+	kasan_init_tags();
 
 	/* KASAN is now initialized, enable it. */
 	static_branch_enable(&kasan_flag_enabled);

mm/kasan/kasan.h

@@ -8,13 +8,31 @@
 #include <linux/kfence.h>
 #include <linux/stackdepot.h>
 
-#ifdef CONFIG_KASAN_HW_TAGS
+#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
 
 #include <linux/static_key.h>
+
+DECLARE_STATIC_KEY_TRUE(kasan_flag_stacktrace);
+
+static inline bool kasan_stack_collection_enabled(void)
+{
+	return static_branch_unlikely(&kasan_flag_stacktrace);
+}
+
+#else /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
+
+static inline bool kasan_stack_collection_enabled(void)
+{
+	return true;
+}
+
+#endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
+
+#ifdef CONFIG_KASAN_HW_TAGS
+
 #include "../slab.h"
 
 DECLARE_STATIC_KEY_TRUE(kasan_flag_vmalloc);
-DECLARE_STATIC_KEY_TRUE(kasan_flag_stacktrace);
 
 enum kasan_mode {
 	KASAN_MODE_SYNC,
@@ -29,11 +47,6 @@ static inline bool kasan_vmalloc_enabled(void)
 	return static_branch_likely(&kasan_flag_vmalloc);
 }
 
-static inline bool kasan_stack_collection_enabled(void)
-{
-	return static_branch_unlikely(&kasan_flag_stacktrace);
-}
-
 static inline bool kasan_async_fault_possible(void)
 {
 	return kasan_mode == KASAN_MODE_ASYNC || kasan_mode == KASAN_MODE_ASYMM;
@@ -46,11 +59,6 @@ static inline bool kasan_sync_fault_possible(void)
 
 #else /* CONFIG_KASAN_HW_TAGS */
 
-static inline bool kasan_stack_collection_enabled(void)
-{
-	return true;
-}
-
 static inline bool kasan_async_fault_possible(void)
 {
 	return false;
@@ -410,6 +418,10 @@ static inline void kasan_enable_tagging(void) { }
 
 #endif /* CONFIG_KASAN_HW_TAGS */
 
+#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
+void __init kasan_init_tags(void);
+#endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
+
 #if defined(CONFIG_KASAN_HW_TAGS) && IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
 
 void kasan_force_async_fault(void);

mm/kasan/sw_tags.c

@@ -42,7 +42,10 @@ void __init kasan_init_sw_tags(void)
 	for_each_possible_cpu(cpu)
 		per_cpu(prng_state, cpu) = (u32)get_cycles();
 
-	pr_info("KernelAddressSanitizer initialized (sw-tags)\n");
+	kasan_init_tags();
+
+	pr_info("KernelAddressSanitizer initialized (sw-tags, stacktrace=%s)\n",
+		kasan_stack_collection_enabled() ? "on" : "off");
 }
 
 /*

mm/kasan/tags.c

@@ -19,6 +19,17 @@
 #include "kasan.h"
 #include "../slab.h"
 
+enum kasan_arg_stacktrace {
+	KASAN_ARG_STACKTRACE_DEFAULT,
+	KASAN_ARG_STACKTRACE_OFF,
+	KASAN_ARG_STACKTRACE_ON,
+};
+
+static enum kasan_arg_stacktrace kasan_arg_stacktrace __initdata;
+
+/* Whether to collect alloc/free stack traces. */
+DEFINE_STATIC_KEY_TRUE(kasan_flag_stacktrace);
+
 /* Non-zero, as initial pointer values are 0. */
 #define STACK_RING_BUSY_PTR ((void *)1)
 
@@ -26,6 +37,38 @@ struct kasan_stack_ring stack_ring = {
 	.lock = __RW_LOCK_UNLOCKED(stack_ring.lock)
 };
 
+/* kasan.stacktrace=off/on */
+static int __init early_kasan_flag_stacktrace(char *arg)
+{
+	if (!arg)
+		return -EINVAL;
+
+	if (!strcmp(arg, "off"))
+		kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
+	else if (!strcmp(arg, "on"))
+		kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
+
+void __init kasan_init_tags(void)
+{
+	switch (kasan_arg_stacktrace) {
+	case KASAN_ARG_STACKTRACE_DEFAULT:
+		/* Default is specified by kasan_flag_stacktrace definition. */
+		break;
+	case KASAN_ARG_STACKTRACE_OFF:
+		static_branch_disable(&kasan_flag_stacktrace);
+		break;
+	case KASAN_ARG_STACKTRACE_ON:
+		static_branch_enable(&kasan_flag_stacktrace);
+		break;
+	}
+}
+
 static void save_stack_info(struct kmem_cache *cache, void *object,
 			gfp_t gfp_flags, bool is_free)
 {