1 files changed, 39 insertions, 1 deletions

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 11a954763be9..4e7cd4c8e687 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -21,6 +21,8 @@
 #include <linux/log2.h>
 #include <linux/memblock.h>
 #include <linux/moduleparam.h>
+#include <linux/notifier.h>
+#include <linux/panic_notifier.h>
 #include <linux/random.h>
 #include <linux/rcupdate.h>
 #include <linux/sched/clock.h>
@@ -67,8 +69,11 @@ static int param_set_sample_interval(const char *val, const struct kernel_param
 	if (ret < 0)
 		return ret;
 
-	if (!num) /* Using 0 to indicate KFENCE is disabled. */
+	/* Using 0 to indicate KFENCE is disabled. */
+	if (!num && READ_ONCE(kfence_enabled)) {
+		pr_info("disabled\n");
 		WRITE_ONCE(kfence_enabled, false);
+	}
 
 	*((unsigned long *)kp->arg) = num;
 
@@ -99,6 +104,10 @@ module_param_named(skip_covered_thresh, kfence_skip_covered_thresh, ulong, 0644)
 static bool kfence_deferrable __read_mostly = IS_ENABLED(CONFIG_KFENCE_DEFERRABLE);
 module_param_named(deferrable, kfence_deferrable, bool, 0444);
 
+/* If true, check all canary bytes on panic. */
+static bool kfence_check_on_panic __read_mostly;
+module_param_named(check_on_panic, kfence_check_on_panic, bool, 0444);
+
 /* The pool of pages used for guard pages and objects. */
 char *__kfence_pool __read_mostly;
 EXPORT_SYMBOL(__kfence_pool); /* Export for test modules. */
@@ -737,6 +746,31 @@ static int __init kfence_debugfs_init(void)
 
 late_initcall(kfence_debugfs_init);
 
+/* === Panic Notifier ====================================================== */
+
+static void kfence_check_all_canary(void)
+{
+	int i;
+
+	for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
+		struct kfence_metadata *meta = &kfence_metadata[i];
+
+		if (meta->state == KFENCE_OBJECT_ALLOCATED)
+			for_each_canary(meta, check_canary_byte);
+	}
+}
+
+static int kfence_check_canary_callback(struct notifier_block *nb,
+					unsigned long reason, void *arg)
+{
+	kfence_check_all_canary();
+	return NOTIFY_OK;
+}
+
+static struct notifier_block kfence_check_canary_notifier = {
+	.notifier_call = kfence_check_canary_callback,
+};
+
 /* === Allocation Gate Timer ================================================ */
 
 static struct delayed_work kfence_timer;
@@ -814,6 +848,9 @@ static void kfence_init_enable(void)
 	else
 		INIT_DELAYED_WORK(&kfence_timer, toggle_allocation_gate);
 
+	if (kfence_check_on_panic)
+		atomic_notifier_chain_register(&panic_notifier_list, &kfence_check_canary_notifier);
+
 	WRITE_ONCE(kfence_enabled, true);
 	queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
 
@@ -874,6 +911,7 @@ static int kfence_enable_late(void)
 
 	WRITE_ONCE(kfence_enabled, true);
 	queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
+	pr_info("re-enabled\n");
 	return 0;
 }