Merge branch 'wireguard-fixes'

Jason A. Donenfeld says:

====================
wireguard fixes for 6.4.2/6.5-rc1

Sorry to send these patches during the merge window, but they're net
fixes, not netdev enhancements, and while I'd ordinarily wait anyway,
I just got a first bug report for one of these fixes, which I originally
had thought was mostly unlikely. So please apply the following three
patches to net:

1) Make proper use of nr_cpu_ids with cpumask_next(), rather than
   awkwardly using modulo, to handle dynamic CPU topology changes.
   Linus noticed this a while ago and pointed it out, and today a user
   actually got hit by it.

2) Respect persistent keepalive and other staged packets when setting
   the private key after the interface is already up.

3) Use timer_delete_sync() instead of del_timer_sync(), per the
   documentation.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 14 deletions

diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
index 125284b..1ea4f87 100644
--- a/drivers/net/wireguard/queueing.h
+++ b/drivers/net/wireguard/queueing.h
@@ -117,20 +117,17 @@ static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
 	return cpu;
 }
 
-/* This function is racy, in the sense that next is unlocked, so it could return
- * the same CPU twice. A race-free version of this would be to instead store an
- * atomic sequence number, do an increment-and-return, and then iterate through
- * every possible CPU until we get to that index -- choose_cpu. However that's
- * a bit slower, and it doesn't seem like this potential race actually
- * introduces any performance loss, so we live with it.
+/* This function is racy, in the sense that it's called while last_cpu is
+ * unlocked, so it could return the same CPU twice. Adding locking or using
+ * atomic sequence numbers is slower though, and the consequences of racing are
+ * harmless, so live with it.
  */
-static inline int wg_cpumask_next_online(int *next)
+static inline int wg_cpumask_next_online(int *last_cpu)
 {
-	int cpu = *next;
-
-	while (unlikely(!cpumask_test_cpu(cpu, cpu_online_mask)))
-		cpu = cpumask_next(cpu, cpu_online_mask) % nr_cpumask_bits;
-	*next = cpumask_next(cpu, cpu_online_mask) % nr_cpumask_bits;
+	int cpu = cpumask_next(*last_cpu, cpu_online_mask);
+	if (cpu >= nr_cpu_ids)
+		cpu = cpumask_first(cpu_online_mask);
+	*last_cpu = cpu;
 	return cpu;
 }
 
@@ -159,7 +156,7 @@ static inline void wg_prev_queue_drop_peeked(struct prev_queue *queue)
 
 static inline int wg_queue_enqueue_per_device_and_peer(
 	struct crypt_queue *device_queue, struct prev_queue *peer_queue,
-	struct sk_buff *skb, struct workqueue_struct *wq, int *next_cpu)
+	struct sk_buff *skb, struct workqueue_struct *wq)
 {
 	int cpu;
 
@@ -173,7 +170,7 @@ static inline int wg_queue_enqueue_per_device_and_peer(
 	/* Then we queue it up in the device queue, which consumes the
 	 * packet as soon as it can.
 	 */
-	cpu = wg_cpumask_next_online(next_cpu);
+	cpu = wg_cpumask_next_online(&device_queue->last_cpu);
 	if (unlikely(ptr_ring_produce_bh(&device_queue->ring, skb)))
 		return -EPIPE;
 	queue_work_on(cpu, wq, &per_cpu_ptr(device_queue->worker, cpu)->work);