netdev - [PATCH net v1] net: io_uring/zcrx: call netdev_queue_get_dma

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Message-ID: <20251028212639.2802158-1-dw@davidwei.uk>
Date: Tue, 28 Oct 2025 14:26:39 -0700
From: David Wei <dw@...idwei.uk>
To: io-uring@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Jens Axboe <axboe@...nel.dk>,
	Pavel Begunkov <asml.silence@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>
Subject: [PATCH net v1] net: io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock

netdev ops must be called under instance lock or rtnl_lock, but
io_register_zcrx_ifq() isn't doing this for netdev_queue_get_dma_dev().

Fix this by taking the instance lock.

Opted to do this by hand instead of netdev_get_by_index_lock(), which is
an older helper that doesn't take netdev tracker.

Signed-off-by: David Wei <dw@...idwei.uk>
---
 io_uring/zcrx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index a816f5902091..55010c0aa7b9 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -606,11 +606,13 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		goto err;
 	}
 
+	netdev_lock(ifq->netdev);
 	ifq->dev = netdev_queue_get_dma_dev(ifq->netdev, reg.if_rxq);
 	if (!ifq->dev) {
 		ret = -EOPNOTSUPP;
-		goto err;
+		goto netdev_unlock;
 	}
+	netdev_unlock(ifq->netdev);
 	get_device(ifq->dev);
 
 	ret = io_zcrx_create_area(ifq, &area);
@@ -640,6 +642,8 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		goto err;
 	}
 	return 0;
+netdev_unlock:
+	netdev_unlock(ifq->netdev);
 err:
 	scoped_guard(mutex, &ctx->mmap_lock)
 		xa_erase(&ctx->zcrx_ctxs, id);
-- 
2.47.3