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-rw-r--r--Documentation/dev-tools/kasan.rst7
-rw-r--r--lib/test_kasan.c2
-rw-r--r--mm/kasan/hw_tags.c29
-rw-r--r--mm/kasan/kasan.h30
-rw-r--r--mm/kasan/report.c2
5 files changed, 52 insertions, 18 deletions
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index 21dc03bc10a4..8089c559d339 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -194,14 +194,17 @@ additional boot parameters that allow disabling KASAN or controlling features:
- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
-- ``kasan.mode=sync`` or ``=async`` controls whether KASAN is configured in
- synchronous or asynchronous mode of execution (default: ``sync``).
+- ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
+ is configured in synchronous, asynchronous or asymmetric mode of
+ execution (default: ``sync``).
Synchronous mode: a bad access is detected immediately when a tag
check fault occurs.
Asynchronous mode: a bad access detection is delayed. When a tag check
fault occurs, the information is stored in hardware (in the TFSR_EL1
register for arm64). The kernel periodically checks the hardware and
only reports tag faults during these checks.
+ Asymmetric mode: a bad access is detected synchronously on reads and
+ asynchronously on writes.
- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
traces collection (default: ``on``).
diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 8835e0784578..ebed755ebf34 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -88,7 +88,7 @@ static void kasan_test_exit(struct kunit *test)
*/
#define KUNIT_EXPECT_KASAN_FAIL(test, expression) do { \
if (IS_ENABLED(CONFIG_KASAN_HW_TAGS) && \
- !kasan_async_mode_enabled()) \
+ kasan_sync_fault_possible()) \
migrate_disable(); \
KUNIT_EXPECT_FALSE(test, READ_ONCE(fail_data.report_found)); \
barrier(); \
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 05d1e9460e2e..dc892119e88f 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -29,6 +29,7 @@ enum kasan_arg_mode {
KASAN_ARG_MODE_DEFAULT,
KASAN_ARG_MODE_SYNC,
KASAN_ARG_MODE_ASYNC,
+ KASAN_ARG_MODE_ASYMM,
};
enum kasan_arg_stacktrace {
@@ -45,9 +46,9 @@ static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;
DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
EXPORT_SYMBOL(kasan_flag_enabled);
-/* Whether the asynchronous mode is enabled. */
-bool kasan_flag_async __ro_after_init;
-EXPORT_SYMBOL_GPL(kasan_flag_async);
+/* Whether the selected mode is synchronous/asynchronous/asymmetric.*/
+enum kasan_mode kasan_mode __ro_after_init;
+EXPORT_SYMBOL_GPL(kasan_mode);
/* Whether to collect alloc/free stack traces. */
DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
@@ -69,7 +70,7 @@ static int __init early_kasan_flag(char *arg)
}
early_param("kasan", early_kasan_flag);
-/* kasan.mode=sync/async */
+/* kasan.mode=sync/async/asymm */
static int __init early_kasan_mode(char *arg)
{
if (!arg)
@@ -79,6 +80,8 @@ static int __init early_kasan_mode(char *arg)
kasan_arg_mode = KASAN_ARG_MODE_SYNC;
else if (!strcmp(arg, "async"))
kasan_arg_mode = KASAN_ARG_MODE_ASYNC;
+ else if (!strcmp(arg, "asymm"))
+ kasan_arg_mode = KASAN_ARG_MODE_ASYMM;
else
return -EINVAL;
@@ -116,11 +119,13 @@ void kasan_init_hw_tags_cpu(void)
return;
/*
- * Enable async mode only when explicitly requested through
- * the command line.
+ * Enable async or asymm modes only when explicitly requested
+ * through the command line.
*/
if (kasan_arg_mode == KASAN_ARG_MODE_ASYNC)
hw_enable_tagging_async();
+ else if (kasan_arg_mode == KASAN_ARG_MODE_ASYMM)
+ hw_enable_tagging_asymm();
else
hw_enable_tagging_sync();
}
@@ -143,15 +148,19 @@ void __init kasan_init_hw_tags(void)
case KASAN_ARG_MODE_DEFAULT:
/*
* Default to sync mode.
- * Do nothing, kasan_flag_async keeps its default value.
*/
- break;
+ fallthrough;
case KASAN_ARG_MODE_SYNC:
- /* Do nothing, kasan_flag_async keeps its default value. */
+ /* Sync mode enabled. */
+ kasan_mode = KASAN_MODE_SYNC;
break;
case KASAN_ARG_MODE_ASYNC:
/* Async mode enabled. */
- kasan_flag_async = true;
+ kasan_mode = KASAN_MODE_ASYNC;
+ break;
+ case KASAN_ARG_MODE_ASYMM:
+ /* Asymm mode enabled. */
+ kasan_mode = KASAN_MODE_ASYMM;
break;
}
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 3639e7c8bb98..b495e17445ad 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -13,16 +13,28 @@
#include "../slab.h"
DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
-extern bool kasan_flag_async __ro_after_init;
+
+enum kasan_mode {
+ KASAN_MODE_SYNC,
+ KASAN_MODE_ASYNC,
+ KASAN_MODE_ASYMM,
+};
+
+extern enum kasan_mode kasan_mode __ro_after_init;
static inline bool kasan_stack_collection_enabled(void)
{
return static_branch_unlikely(&kasan_flag_stacktrace);
}
-static inline bool kasan_async_mode_enabled(void)
+static inline bool kasan_async_fault_possible(void)
+{
+ return kasan_mode == KASAN_MODE_ASYNC || kasan_mode == KASAN_MODE_ASYMM;
+}
+
+static inline bool kasan_sync_fault_possible(void)
{
- return kasan_flag_async;
+ return kasan_mode == KASAN_MODE_SYNC || kasan_mode == KASAN_MODE_ASYMM;
}
#else
@@ -31,11 +43,16 @@ static inline bool kasan_stack_collection_enabled(void)
return true;
}
-static inline bool kasan_async_mode_enabled(void)
+static inline bool kasan_async_fault_possible(void)
{
return false;
}
+static inline bool kasan_sync_fault_possible(void)
+{
+ return true;
+}
+
#endif
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
@@ -287,6 +304,9 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
#ifndef arch_enable_tagging_async
#define arch_enable_tagging_async()
#endif
+#ifndef arch_enable_tagging_asymm
+#define arch_enable_tagging_asymm()
+#endif
#ifndef arch_force_async_tag_fault
#define arch_force_async_tag_fault()
#endif
@@ -302,6 +322,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
#define hw_enable_tagging_sync() arch_enable_tagging_sync()
#define hw_enable_tagging_async() arch_enable_tagging_async()
+#define hw_enable_tagging_asymm() arch_enable_tagging_asymm()
#define hw_force_async_tag_fault() arch_force_async_tag_fault()
#define hw_get_random_tag() arch_get_random_tag()
#define hw_get_mem_tag(addr) arch_get_mem_tag(addr)
@@ -312,6 +333,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
#define hw_enable_tagging_sync()
#define hw_enable_tagging_async()
+#define hw_enable_tagging_asymm()
#endif /* CONFIG_KASAN_HW_TAGS */
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 884a950c7026..9da071ad930c 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -112,7 +112,7 @@ static void start_report(unsigned long *flags)
static void end_report(unsigned long *flags, unsigned long addr)
{
- if (!kasan_async_mode_enabled())
+ if (!kasan_async_fault_possible())
trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
pr_err("==================================================================\n");
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.