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-rw-r--r--lib/Kconfig.kfence1
-rw-r--r--mm/kfence/core.c45
2 files changed, 30 insertions, 16 deletions
diff --git a/lib/Kconfig.kfence b/lib/Kconfig.kfence
index 78f50ccb3b45..e641add33947 100644
--- a/lib/Kconfig.kfence
+++ b/lib/Kconfig.kfence
@@ -7,6 +7,7 @@ menuconfig KFENCE
bool "KFENCE: low-overhead sampling-based memory safety error detector"
depends on HAVE_ARCH_KFENCE && (SLAB || SLUB)
select STACKTRACE
+ select IRQ_WORK
help
KFENCE is a low-overhead sampling-based detector of heap out-of-bounds
access, use-after-free, and invalid-free errors. KFENCE is designed
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;