netdev - [PATCH net] sfc: Do not free an empty page

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Date:   Mon, 04 Apr 2022 11:48:51 +0100
From:   Martin Habets <habetsm.xilinx@...il.com>
To:     kuba@...nel.org, pabeni@...hat.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, ap420073@...il.com, ecree.xilinx@...il.com
Subject: [PATCH net] sfc: Do not free an empty page_ring

When the page_ring is not used page_ptr_mask is 0.
Do not dereference page_ring[0] in this case.

Fixes: 2768935a4660 ("sfc: reuse pages to avoid DMA mapping/unmapping costs")
Reported-by: Taehee Yoo <ap420073@...il.com>
Signed-off-by: Martin Habets <habetsm.xilinx@...il.com>
---
 drivers/net/ethernet/sfc/rx_common.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/sfc/rx_common.c b/drivers/net/ethernet/sfc/rx_common.c
index 1b22c7be0088..fa8b9aacca11 100644
--- a/drivers/net/ethernet/sfc/rx_common.c
+++ b/drivers/net/ethernet/sfc/rx_common.c
@@ -150,6 +150,9 @@ static void efx_fini_rx_recycle_ring(struct efx_rx_queue *rx_queue)
 	struct efx_nic *efx = rx_queue->efx;
 	int i;
 
+	if (unlikely(!rx_queue->page_ring))
+		return;
+
 	/* Unmap and release the pages in the recycle ring. Remove the ring. */
 	for (i = 0; i <= rx_queue->page_ptr_mask; i++) {
 		struct page *page = rx_queue->page_ring[i];