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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Taehee Yoo <ap420073@gmail.com>,
        Martin Habets <habetsm.xilinx@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.16 178/285] sfc: Do not free an empty page_ring
Date:   Tue, 12 Apr 2022 08:30:35 +0200
Message-Id: <20220412062948.804765167@linuxfoundation.org>
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From: Martin Habets <habetsm.xilinx@gmail.com>

[ Upstream commit 458f5d92df4807e2a7c803ed928369129996bf96 ]

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@gmail.com>
Signed-off-by: Martin Habets <habetsm.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 633ca77a26fd..b925de9b4302 100644
--- a/drivers/net/ethernet/sfc/rx_common.c
+++ b/drivers/net/ethernet/sfc/rx_common.c
@@ -166,6 +166,9 @@ 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];
-- 
2.35.1