[PATCH net] xsk: freeze deferred pool teardown without blocking unregister

[PATCH net] xsk: freeze deferred pool teardown without blocking unregister

[James Hilliard]

Deferred pool destruction calls ndo_bpf() under RTNL. system_wq is
not frozen during system sleep, so that callback can run after a
device has suspended and gated its clocks. Use system_freezable_wq
so running destruction finishes before device suspend and new work
waits until process thaw.

Keep assigned pools visible to NETDEV_UNREGISTER independently of
the socket list. A released socket has already left that list, but
its final pool put can queue destruction after workqueues freeze.
A resume-time unregister would then wait for a device reference
whose release cannot run until the resume completes.

Track assigned pools under RTNL and detach remaining pools after the
notifier socket walk, including copy-mode pools. Remove the entry on
assignment failure and normal teardown. The deferred worker still
owns the pool and later observes the cleared device pointer, avoiding
a second driver detach or device put.

Fixes: 1c1efc2af158 ("xsk: Create and free buffer pool independently from umem")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 include/net/xsk_buff_pool.h |  3 +++
 net/xdp/xsk.c               |  4 ++++
 net/xdp/xsk_buff_pool.c     | 25 ++++++++++++++++++++++++-
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index a7df573784fd..cea6e883f7cd 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -48,6 +48,8 @@ struct xsk_buff_pool {
 	struct device *dev;
 	struct net_device *netdev;
 	struct list_head xsk_tx_list;
+	/* Assigned pools, including deferred releases; protected by RTNL. */
+	struct list_head dev_list;
 	/* Protects modifications to the xsk_tx_list */
 	spinlock_t xsk_tx_list_lock;
 	refcount_t users;
@@ -119,6 +121,7 @@ bool xp_put_pool(struct xsk_buff_pool *pool);
 void xp_clear_dev(struct xsk_buff_pool *pool);
 void xp_add_xsk(struct xsk_buff_pool *pool, struct xdp_sock *xs);
 void xp_del_xsk(struct xsk_buff_pool *pool, struct xdp_sock *xs);
+void xp_clear_dev_all(struct net_device *dev);
 
 /* AF_XDP, and XDP core. */
 void xp_free(struct xdp_buff_xsk *xskb);
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 33475b180ea6..a2ae0e10d893 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -2145,6 +2145,10 @@ static int xsk_notifier(struct notifier_block *this,
 			mutex_unlock(&xs->mutex);
 		}
 		mutex_unlock(&net->xdp.lock);
+		/* A released socket is no longer on xdp.list. Its pool can still
+		 * hold a device reference on the frozen release workqueue.
+		 */
+		xp_clear_dev_all(dev);
 		break;
 	}
 	return NOTIFY_DONE;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 9d2d94f1fb75..b5fd0850db5b 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -12,6 +12,11 @@
 
 #define ETH_PAD_LEN (ETH_HLEN + 2 * VLAN_HLEN  + ETH_FCS_LEN)
 
+/* Socket removal precedes the final pool put. Keep assigned pools visible to
+ * NETDEV_UNREGISTER even while their release work is waiting for process thaw.
+ */
+static LIST_HEAD(xsk_dev_pools);
+
 void xp_add_xsk(struct xsk_buff_pool *pool, struct xdp_sock *xs)
 {
 	if (!xs->tx)
@@ -204,6 +209,7 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 	pool->cached_need_wakeup = XDP_WAKEUP_TX;
 
 	dev_hold(netdev);
+	list_add_tail(&pool->dev_list, &xsk_dev_pools);
 
 	if (force_copy)
 		/* For copy-mode, we are done. */
@@ -265,6 +271,8 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 		err = 0; /* fallback to copy mode */
 	if (err) {
 		xsk_clear_pool_at_qid(netdev, queue_id);
+		list_del(&pool->dev_list);
+		pool->netdev = NULL;
 		dev_put(netdev);
 	}
 	return err;
@@ -291,17 +299,29 @@ void xp_clear_dev(struct xsk_buff_pool *pool)
 {
 	struct net_device *netdev = pool->netdev;
 
+	ASSERT_RTNL();
 	if (!pool->netdev)
 		return;
 
 	netdev_lock_ops(netdev);
 	xp_disable_drv_zc(pool);
 	xsk_clear_pool_at_qid(pool->netdev, pool->queue_id);
+	list_del(&pool->dev_list);
 	pool->netdev = NULL;
 	netdev_unlock_ops(netdev);
 	dev_put(netdev);
 }
 
+void xp_clear_dev_all(struct net_device *dev)
+{
+	struct xsk_buff_pool *pool, *next;
+
+	ASSERT_RTNL();
+	list_for_each_entry_safe(pool, next, &xsk_dev_pools, dev_list)
+		if (pool->netdev == dev)
+			xp_clear_dev(pool);
+}
+
 static void xp_release_deferred(struct work_struct *work)
 {
 	struct xsk_buff_pool *pool = container_of(work, struct xsk_buff_pool,
@@ -337,7 +357,10 @@ bool xp_put_pool(struct xsk_buff_pool *pool)
 
 	if (refcount_dec_and_test(&pool->users)) {
 		INIT_WORK(&pool->work, xp_release_deferred);
-		schedule_work(&pool->work);
+		/* Teardown calls ndo_bpf(), which may need powered hardware.
+		 * RTNL alone does not exclude the device's system PM callbacks.
+		 */
+		queue_work(system_freezable_wq, &pool->work);
 		return true;
 	}
 

---
base-commit: a7bfaba4823e3c165bb2004c74eff7c096672bc7
change-id: 20260930-xsk-suspend-teardown-902f98408c93

Best regards,
--  
James Hilliard <james.hilliard1@gmail.com>

Re: [PATCH net] xsk: freeze deferred pool teardown without blocking unregister

[netdev-bot+sinfo]

Hi!

This is an automated message. This series looks like a fix, but its
commit messages seem to be missing some information:

 - How the issue was discovered, e.g. hit in production, hit during
   development, syzbot report, manual code inspection, LLM or static
   analysis tool scan.

 - Whether the issue was actually triggered, or is only theoretical
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Please do not repost the series just to address the above. Instead,
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