1 files changed, 29 insertions, 16 deletions

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 768dbd58170d..235d726f88bc 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -10,6 +10,7 @@
 #include <linux/atomic.h>
 #include <linux/bug.h>
 #include <linux/debugfs.h>
+#include <linux/irq_work.h>
 #include <linux/kcsan-checks.h>
 #include <linux/kfence.h>
 #include <linux/kmemleak.h>
@@ -587,6 +588,17 @@ late_initcall(kfence_debugfs_init);
 
 /* === Allocation Gate Timer ================================================ */
 
+#ifdef CONFIG_KFENCE_STATIC_KEYS
+/* Wait queue to wake up allocation-gate timer task. */
+static DECLARE_WAIT_QUEUE_HEAD(allocation_wait);
+
+static void wake_up_kfence_timer(struct irq_work *work)
+{
+	wake_up(&allocation_wait);
+}
+static DEFINE_IRQ_WORK(wake_up_kfence_timer_work, wake_up_kfence_timer);
+#endif
+
 /*
  * Set up delayed work, which will enable and disable the static key. We need to
  * use a work queue (rather than a simple timer), since enabling and disabling a
@@ -604,25 +616,13 @@ static void toggle_allocation_gate(struct work_struct *work)
 	if (!READ_ONCE(kfence_enabled))
 		return;
 
-	/* Enable static key, and await allocation to happen. */
 	atomic_set(&kfence_allocation_gate, 0);
 #ifdef CONFIG_KFENCE_STATIC_KEYS
+	/* Enable static key, and await allocation to happen. */
 	static_branch_enable(&kfence_allocation_key);
-	/*
-	 * Await an allocation. Timeout after 1 second, in case the kernel stops
-	 * doing allocations, to avoid stalling this worker task for too long.
-	 */
-	{
-		unsigned long end_wait = jiffies + HZ;
-
-		do {
-			set_current_state(TASK_UNINTERRUPTIBLE);
-			if (atomic_read(&kfence_allocation_gate) != 0)
-				break;
-			schedule_timeout(1);
-		} while (time_before(jiffies, end_wait));
-		__set_current_state(TASK_RUNNING);
-	}
+
+	wait_event_timeout(allocation_wait, atomic_read(&kfence_allocation_gate), HZ);
+
 	/* Disable static key and reset timer. */
 	static_branch_disable(&kfence_allocation_key);
 #endif
@@ -729,6 +729,19 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
 	 */
 	if (atomic_read(&kfence_allocation_gate) || atomic_inc_return(&kfence_allocation_gate) > 1)
 		return NULL;
+#ifdef CONFIG_KFENCE_STATIC_KEYS
+	/*
+	 * waitqueue_active() is fully ordered after the update of
+	 * kfence_allocation_gate per atomic_inc_return().
+	 */
+	if (waitqueue_active(&allocation_wait)) {
+		/*
+		 * Calling wake_up() here may deadlock when allocations happen
+		 * from within timer code. Use an irq_work to defer it.
+		 */
+		irq_work_queue(&wake_up_kfence_timer_work);
+	}
+#endif
 
 	if (!READ_ONCE(kfence_enabled))
 		return NULL;